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Riko…I'm going with you…to the bottom of the Abyss.


Reg is a robot who appears to be a little boy. His actual age, origins, and even name are unknown because he cannot recall anything about his life before his encounter with Riko. He is named after a dog Riko used to have.[1]

Having an artificial body, Reg might be the only being completely immune to the Curse of the Abyss. Because of this, he is sometimes referred to as "The Treasure of the Deep."

According to Garburune, Reg could be an Interference Unit of one of the lower layers.


Reg has tanned skin and dark hair. He wears a metal helmet with two asymmetrical horns protruding out of the sides and what appears to be a glass lens in the front,which displays the number of Incinerator charges he has left to use. Underneath his helmet is a jagged metal headband of some sort, with bolts on either side keeping it in place on his head. His ears are slightly pointed. Reg's eyes are yellow, and his pupils are catlike, vertical slits. There are two red patches of skin on his cheeks, and four more on either side of his rib cage. His eyebrows are small and gray. Though he is a robot, the only parts of him that appear to be mechanical are his arms and legs, which are bulky compared to the rest of his body. He has nipples, a belly button, and even human genitals.

He is usually shirtless, save for the tattered red cape he is wearing when Riko finds him. His washed-out green and purple pants are baggy and stop just below his knees.

He later loses an arm and earns a scar on his belly button after his fight with Bondrewd. [2][3]


Despite being a formidable fighter, Reg is rather shy, naive, and unassertive. He blushes easily and often cries when in distress. However, when forced into danger or an unpleasant situation, he is shown to be hot-tempered and sharp, compared to Riko's analytic, noncombatant role. Regardless of his skittishness, Reg has made it his sworn duty to protect Riko and doesn't hesitate to put up a fight when she is in harm's way.

According to Ozen, the way he speaks and handles his body is similar to Lyza. One of his favorite words to say is "irredeemable," which was a word that Lyza said often.[4]

History Edit

Spoiler warning: The following section contains spoilers. Read with caution.

Early Life Edit

Very little is known of Reg's past, as he remembers nothing before meeting Riko. Reg is found by Riko in the Abode of Fossils at a depth of 100–220 meters after he used his incinerator to save Riko's life.[5]

He and Riko presume he is from the bottom of the Abyss, as one of Lyza's sketches depicts a robot-like creature from the pit that heavily resembles him. According to Lyza's notes, she first encountered the creature around the 7th layer.[6] He has at one point before met Ozen the Unmovable[citation needed], as well as supposedly been close to Faputa[7], though he doesn't remember knowing either of them. As he descends further into the Abyss, Reg's memories come back in little snippets at a time. He eventually recalls that at some point he had journeyed alongside Lyza, though he does not remember any specific details about her.[citaion needed] According to Faputa, Reg's name was Reg even before he met Riko.[8]

Orth ArcEdit

While collecting Artifacts in the Abyss's 1st layer, Riko is being chased by a Crimson Splitjaw. When a beam of energy hits the Splitjaw and chases it away, a curious Riko follows the wreckage from the beam to its source, where she finds an unconscious robot boy. Upon further inspection, Riko realizes he is not human, and with the help of Nat, she brings him out of the Abyss and back to Belchero Orphanage. There she studies and takes notes on Reg's body and is able to wake him up using a jolt of electricity. She names the robot Reg after a dog she used to own, helps him settle in at the orphanage, and tells him about Orth and the Abyss.[9]

During the Resurrection Festival, a celebration of returning Delvers[debatable], Hablog returns from the Abyss with Riko's mother's White Whistle along with some of Lyza's field notes. While Riko and Reg look through them, they notice one of them contains a sketch of a figure that looks similar to Reg, along with a letter that states that Lyza is waiting for her daughter at the bottom of the Abyss. Riko decides to leave Orth and go to the bottom of the Abyss, and Reg decides to go with her. Before leaving, Reg visits Kiyui in his room to say goodbye and warn him not to look in the mirror on his birthday. Then he and Riko leave the orphanage in the middle of the night with Nat and Shiggy to see them off. When they reach the Wharf district, a part of Orth that dips into the Abyss, Riko and Reg say their final goodbyes to Nat and Shiggy, and begin their descent towards the bottom of the world.[10]

Descent to the Abyss ArcEdit

After the sad goodbyes from Riko and Reg to Nat and Shiggy, they finally descend and land somewhere in the first layer of the Abyss, with a depth of 820 meters.[11] While they are eating their breakfast, Riko notices Jiruo stuck a red slip with the contents of Lyza's sealed letter and the message, "I'll depart at dawn to capture you", into their belongings: Riko rushes and packs their things with Reg's help, and they leave the premises post-haste.[12] Immediately afterwards, they land in a Silkfang's territory and are ambushed by it; however, they escape while defending themselves.[13] They witness the 2nd layer for the first time. Reg suddenly hears his own voice—something about his past–and later, he accompanies Riko for a short break. While they are having a conversation, Reg sees a Delver above some boulders who chases them while they rush to escape and hide—Reg defends Riko. Not very much later, the delver catches up—and is revealed to be the Black Whistle Delver Hablog, who was impressed by the group's fast pace. Hablog's main objective was to meet and inspect Reg, because Nat and Shiggy told him about Reg's true nature. Instead of taking them back to Orth, he offers to escort them to the Seeker Camp, which Riko declines. He then gives Riko a warning about Ozen, some medicine, and other supplies and lets them go.[14]

Shortly after they arrive on the 2nd layer, Riko and Reg hear a cry for help, but it's one of a Corpse-Weeper, which mimics its victims cries of pain and fear: they follow it. While observing the Corpse-Weeper, they are ambushed by a colony of them, and one of them snatches Riko. She struggles initially, but she loses consciousness due to the strain of ascension. Reg, unsure of what to do, recalls his memory of using the Incinerator to save Riko from the Crimson Splitjaw in the 1st layer. Instinctively, he raises his arm and fires his Incinerator, obliterating the colony of Corpse-Weepers and saving Riko from being fed to the Corpse-Weeper's young.[15]

Seeker Camp Arc Edit

After a short climb down the top of the 2nd layer, Reg and Riko find themselves in the company of the Immovable Lord, Ozen, at the Seeker Camp; her domain is to supervise descent past the 2nd layer. While in the presence of Ozen; Riko and Reg make friends with Marulk, Ozen's pupil and servant. Later on, Riko learns from Ozen about her birth in the Abyss and that she was a stillborn that only survived due to the Curse-Warding Box.[16]

Ozen continues to agonize Riko by assuming she probably also will stop moving at some point. Hearing that, Regs steps in and tells Ozen that she has gone too far and a fight erupts between them, one-sidedly in Ozen's favor, Reg arrives at the conclusion that only a shot from his Incinerator will be able to beat Ozen. Than he tries he misses his shot and Ozen stomps him until he fells unconscious as Riko can do nothing but helplessly watch.

During the time Reg is unconscious, Marulk had panicked and went to get the other Subterranean Bandits to stop the fight. Afterward, it's reveald that Ozen was trying to provoke Reg and Riko into a fight in order to test if they are ready to make their way further down The Abyss. She tells them that Riko's lack of communication in battle, as well as Reg's lack of being able to judge the right timing to use his Incinerator are fatal flaws that would have them wind up dead sooner or later. Furthermore, because Reg falls unconscious within ten minutes after using his Incinerator, Riko needs to be able to protect herself. As such, she instructs both of them to stay three weeks in the forest behind the Seeker Camp as survival training.

During their survival training Riko and Reg learn to be more adapt and aware of their strengths and weaknesses. Reg and Riko return to the Seeker Camp after ten days and Marulk congratulates them on passing as most people don't even manage tomake it even a week. Ozen tells Reg and Riko that the training camp also should have helped both of them to train to keep track on time due to The Abyss causing a person's sense of time to get lost. Afterward, Riko and Reg leave the Seeker Camp to advance down to the 3rd layer.

The Great Fault Arc Edit

Riko and Reg descend through the 3rd layer, the Great Fault, which features a long, vertical shaft. The trip is made more dangerous by the Madokajack constantly seeking prey. Fortunately, there are plenty of Neritantan who make nests in holes along the shaft. Riko uses them as distractions to draw the predators away. Riko and Reg run into the very same Crimson Splitjaw that Reg saved Riko from previously. Reg recalls Ozen's warning: using the Incinerator causes Reg to fall asleep within ten minutes, and for two hours afterward, it is impossible to wake him up. This would leave Riko completely unprotected, so if Reg uses the Incinerator, he must make absolutely sure that he defeats the threat before him. Riko recalls that the Crimson Splitjaw eats Artifacts, so she throws one to distract it, allowing Reg to attack from below. He knocks the Crimson Splitjaw into the shaft, where it is attacked by several Madokajack.

Poison and Soul Liberation Arc Edit

During Riko's and Reg's descent to the 4th layer they are attacked by an Orb Piercer. Druing the battle Riko's hand gets stabbed by one of the Orb Piercer's venomous needles, causing her to hallucinate and, in combination with the curse due to ascending to fast in retreat, starts bleeding out of every hole in her body. Shortly afterward she looses conscious leaving Reg in despair.

Nanachi reveals themself to Reg, due to seeing him crying over Riko's body. Because the two's relationship reminds Nanachi of their relationship with Mitty, Nanachi decides to aid them. With Nanachi's help Reg starts to gather the ingredients needed to cure Riko. During the gathering he encounters the Orb Piercer again and, thanks to the help of Nanachi via a communicator, is able to ward it off with a beam from his Incinerator. Nanachi, surprised by the power of it and similarity to Bondrewd's Sparagmos, asks Reg to kill Mitty with it to end her suffering.

Reg, though conflicted, follows Nanachi's wish and comforts them afterward as they break down in tears due to setting Mitty free, but also losing her. After Riko recovered, Nanachi decides to join Riko and Reg on their journey to the bottom of the Abyss.

Ido Front Arc Edit

After preparations, the group embarks from Nanachi's hideout, reaching the field of Eternal Fortunes. There they encounter one of Bondrewd's Umbra Hands. A brief exchange follows, in which the Umbra Hand tells them that Bondrewd is expecting them. Then the three of them reach Bondrewd's base, Ido Front. A girl, Prushka, approaches them and asks if they are her father's guests. A few moments later Bondrewd arrives, greets the trio and informs them that entrance into the 6th layer is only possible with a personalized White Whistle.

He invites them to stay a night and Prushka gives them a tour of the base. Druing the night, Reg is taken away by the Umbra Hands and they start running tests on him. They even cut off his arm to further analyse it. Nanachi, Riko, and Pruhska find him due to hearing his screams in the hall. Prushka orders the Umbra Hands to stop treating her father's guests that way, only to be informed by them that this area is off limits for her. The Trio, together with Prushka, escapes outside the Ido Front and tries to escape in a boat.

Only Prushka stays back because she wants to convince Bondrewd to return Reg's arm. Shortly afterward, Reg, Nanachi, and Riko are confronted by Bondrewd and his Umbra Hands again, however they have been let into a trap by the trio and are attacked by a Stingerhead.Only Bondrewd survives the attack with his Sparagmos, but is dispatched by a clever strategy of Nanachi and Reg resulting in him being exposed to the curse as well crushed by Reg with a boulder. Moments later Prushka and an Umbra Hand arrive. Prushka bursts out in tears over the state Bondrewd is in. The Umbra Hand quickly removes Bondrewd's mask and replaces it with his own, leading him to turn into Bondrewd in the process.

Bondrewd makes the relieved Prushka pass out and reveals to the trio that all Umbra Hands are copies of him he can transfer his consciousness into. After a quick beatdown he leaves them and invites them back to the Ido Front whenever they are ready. Riko notes that Bondrewd maybe uses the artifact, Zoaholic, to transfer parts of his consciousness. Together with Reg the both make a strategy in order to destroy it. As they sneak back into Ido Front Nanachi and Riko make their way into what Nanachi calls the processing room, while Reg searches for the power plant to destroy it. During that he is seemingly overloaded and wents out of control. He makes his way back into Ido Front and interrupts the conversation between Bondrewd, Nanachi and Riko by attacking Bondrewd.

A fight between Reg and Bondrewd breaks out. The out of control Reg blasts his Incinerator without consideration for the surroundings, but Bondrewd is able to keep up with him. Only due to Nanachi's interruption, due to not wanting to see Reg in such a state and begging him to stop with a hug, the fight comes to a momentarily halt; with Reg turning back to his usual self. During the second stage of the fight, Bondrewd reveals that he turned Prushka into a cartridge. This revelation causes Riko to be shaken up to tears because Prushka was a good friend to her and enrages Reg. After Bondrewd's defeat, resulting him to be cut in half, Riko holds Prushka's cartridge close to her and cries. In that moment a stone, like one needed to craft a personal White Whistle, comes out of the cartridge.

Nanachi tells Riko that Prushka most likely assumed the form of the stone to be able to travel along with Riko, which relieves Riko abit. Nanachi makes a harness so Riko can wear Prushka's stone around her neck. As the group gets ready to traverse into the 6th layer, it is shown that Bondrewd's consciousness still lives on within his Umbra Hands as they come to see Riko's group off.

Ilblu Arc Edit

Riko's group uses the altar connecting the 5th to the 6th layer. On their way down, they see various creatures and later, after leaving the elevator, decide to make a camp for the night. Nanachi awakens and notices something invaded the camp after they had fallen asleep and stole Prushka's stone. With the help of Meinya, they track it down to a village.

The being that took the stone introduces itself as Majikaja and tells them that it only took Prushka's stone to get it worked on by a jeweler in order to make it into its finalized form. While they are waiting, Majikaja explains a few things about the village, Ilblu, and brings them to a market. Due to an accident, Meinya is injured by a very curious Narehate and the group witnesses the village's ritual to balance value. In the ritual the narehate at fault for Meinya being hurt gets stripped off it's belongings and even parts of its skin. Afterward, they manage to stay at a hotel but split up after hearing a loud sound that Reg wants to investigate, while Nanachi and Riko stay behind.

As Reg follows the sound he meets the Narehate Princess; Faputa and her guardian, Garburune. Faputa is quick to approach Reg without hesitation, seemingly having known him before he lost his memories. Uppon finding out he forgot her she is shaken and takes him away to further examine him. A brief exchange between them follows in which Faputa insists that Reg's name always has been Reg, but Reg refuses to accept that; saying that he is Reg because Riko gave him that name. He leaves her and starts making is way back to the village. During is way back he is assaulted by a Ryuusazai but Garburune rescues him.

The both have a short chat and Garburune tells Reg that he is an Interference Unit similar to themself. Afterward, Reg continues to make his way back to the village and uppon suddenly hearing Riko's whistle dashes to her side to protect her from the Fuzosheppu. As he lunges at the creature, it collapses and Wazukyan shows up telling Riko and Reg that the Fuzosheppu is already dead and explains the nature of it. Riko asks him if he knows of a way to get enough value to buy back Nanachi from Belaf. Wazukayn tells them that if they had a body part of Faputa it might be possible and Reg decides to go ask her. After making his way back to Faputa Reg tells her about the situation with his friend Nanachi and asks her for help. Faputa agrees to give Reg a part of her if he keeps his promise. Uppon asking for more information on the promise between them Faputa rips one of her ears and arms off, happily handing them to Reg telling him "Let's eradicate them togther, Reg."

Reg, taken aback by her request, asks what she means by that and Faputa specifies she wants him to be her "helper", because she knows Reg is too kind to destroy the village. In the past, Reg told her his incinerator has the power to "rewrite" the laws stopping Faputa from entering the village and as such she wants him to do so in return for her body parts. Reg and Faputa start making their way back to the village, but because creatures are attracted by the smell of her blood, Garburune stays behind to fend them off.

As they arrive at the entrance of the village, Riko comes to greet Reg and catches a glimpse of Faputa. Immediately after Reg steps inside the barrier with Faputa's body parts, the village reacts similar to the Ilblu Summoning, but far stronger and more uncontrolled.

Reg panics and contemplates to bring the parts to Belaf right away, but is stopped by Vueko because she assumes seeing them could drive Belaf insane. When Vueko asks Reg how he acquired the parts, Reg tells her Faputa gave them to him so that he would fulfill his promise. Wazukyan, who had eavesdropped the conversation, concludes Reg must have been "The Prince" and is surprised Reg managed to secure parts of "The Princess". He also casually greets Vueko, expresses his joy of her finally being able to leave her pit, and asks her if she already told them about "The Princess". Vueko reluctantly confirms she has, but notes she told the story from her point of view.

After the conversation between Wazukyan, Riko and the villagers, Juroimoh shows up and starts attacking. Wazukyan quickly grabs Vueko and moves to a higher position to avoid Juroimoh. Reg manages to draw Juroimoh's attention and a fight erupts between them, which leads to Juroimoh transforming into a gooey, even more monstrous, form.



The Incinerator (火葬砲: Cremation Cannon) is a powerful incendiary cannon built into hands and feet. Any object in its path disappears, "as if it comes undone... Shortly afterwards, the surrounding air ignites to nothing." The incinerator is also capable of "tensing up" the force field of the Abyss in an undefined manner.[17] The size of the beam changes depending on Reg's will.[18] It is important to note that the Incinerator does not just burn objects; it is connected to the Abyss in an unknown way. The name implies that everything hit by the light returns to the Abyss. For instance, when Reg kills Mitty, he makes a comment about Mitty's soul "cycling again." Nanachi also comments that Reg's Incinerator "has the power to rewrite the rules of the Abyss".[19] This weapon seems to work similarly to Sparagmos, the Origin-Guiding Light.

The Incinerator is a Relic that is part of Reg. All Relics in the Abyss contain a pattern that signify the number of uses left before becoming useless. Along with passing out for 2 hours after 10 minutes after using the Incinerator, the pattern in Reg's helmet decreases.[20] Electricity seems to recharge it, as the symbol grew again after Reg was exposed to electricity at Ido Front.

It could also be possible that when over used and he runs out of energy he loses his memory. This would explain why Riko was able to wake him up with a jolt of electricity.

Extendable ArmsEdit

Reg's arms can extend up to 40 meters each. He can shoot them to the top of cliffs or grab things very far away. The cord attaching them is very durable. Using these arms does not reduce the pattern on Reg's helmet because they require a minimal amount of energy.

Heightened SensesEdit

Reg's senses of smell and hearing are stronger than that of a human's. Nanachi has commented to themself that he reminds them of a dog by the way he follows his nose.[21] He feels simulated pain.

Super DurabilityEdit

As commented on by several characters, Reg's body is extremely durable, even to the point that Ozen the Unmovable couldn't break him even when slamming him into the floor with all her strength.[22] Despite his high durability, Reg is agile and weighs little. His wounds heal at a faster rate than a human's, and he has a very high pain tolerance. His navel is the thinnest part of his skin, making it a weak spot.

Trivia Edit

Good boy

Reg the dog and young Riko

  • Reg is often associated with dogs. He is named after a dog Riko had when she was younger, and is also sometimes compared to a dog, even by those who aren't aware of the origin of his name.
  • He is slightly disappointed that his muscles won't grow.
  • He is able to get erections, despite being a robot.
  • Akihito stated in an interview that Reg was inspired by a Cave Story character named Quote.
  • His favorite food is Mustard Manjuu.[23]
  • Reg's design comes from "the familiar shape and ruggedness of a robot, as well as the sexy defenselessness of Astro Boy"[24]


  1. chapter 4, page 14
  2. Chapter 31, page 2
  3. Chapter 37, page 31
  4. extra chapter 3, page 4
  5. chapter 2, page 16
  6. chapter 6, page 2
  7. chapter 42, page 14
  8. chapter 42, page 21
  9. chapters 2–4
  10. chapters 5–8
  11. chapter 9, page 3
  12. chapter 9, pages 9–12
  13. chapter 9, pages 12–14
  14. chapter 9, page 17–chapter 10, page 10
  15. chapters 10, 11
  16. chapters 12–17
  17. Chapter 35, Page 7
  18. Chapter 11, Page 15 For comparisons, see: - Chapter 35, page 14 - Chapter 2, Page 14 - Chapter 15, Page 16
  19. Chapter 29, Page 14
  20. Volume 4, Chapter 29, Pages 13-14
  21. Chapter 39, Page 36
  22. Chapter 16, Page 5
  23. Volume 6 extras
  24. Doorbeetle Reco
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