Jiruo

Jiruo (known as Leader by his students) is a Moon Whistle Delver who serves as a teacher for apprentice delvers from the Belchero Orphanage in the town of Orth. While he works as an instructor for the children, he's also largely responsible for their upbringing and well-being.

Appearance
A young man with white hair and bright blue eyes, average height. He is almost always frowning. He wears a typical delver's gear.

Personality
Jiruo is serious and stern and tends to come off as cold at times, but it's only because he takes his job as a teacher and instructor seriously, and prioritizes the childrens' safety above all else. At times he's very insightful and gives good advice, and does his best to support Riko after her mother's whistle was brought back to the surface.

Early life
He was the apprentice of the legendary white whistle Lyza "The Annihilator." Though he was only a red whistle at the time, before she made her last dive, Lyza entrusted him with watching over Riko and protecting her identity as a white whistle's child.

Orth Arc
Jiruo is present during a briefing in the orphanage where he tells the children about the new rules applied to their delving studies, which include delving alone in assigned areas. Then the head of the orphanage, Belchero, speaks with the apprentice delvers, emphasizing that any of the valuable objects in The Abyss, called Artifacts, are to be turned in to the orphanage if recovered, to provide funding for the orphanage’s continued operation. After the briefing, the apprentices are assigned delving areas, Riko being assigned the same place she delved the last time, driving her to try to convince Jiruo to assign her a deeper one. However, he disagrees, explaining that delving in the previous area would be more efficient. Riko then explains her dream of becoming a White Whistle to her teacher, so that she could see her mother again. Jiruo, though still disagreeing, promises to grant Riko's request if she manages to find artifacts with the most value on the next day’s trip.

After Riko and her friends cause a blackout in the orphanage, than trying to awake Reg viva an electrical shock, Jiruo seeks out the source of it by investigating rooms. Only a few seconds later he is already heard yelling at Riko's door, asking for Riko to come out and explain. However, he rushes into the room almost immediately, ignoring Riko's explanation. Noticing something under a sheet, Jiruo immediately removes it, but only finds the electrical device attached to a helmet, to Riko's surprise. The teacher then turns to Riko, asking about what she has to say. Riko replies weakly that she will not do so again. As Leader begins lecturing Riko, she spots Ref dangling from the ceiling, through a rope extending from his left arm, watching, though the boy quickly pulls himself up the rope, disappearing into the ceiling again upon noticing Riko spotting him. Jiruo then notices Riko not paying attention to him, thus pulls her away to receive her punishment.

Later on, because they would't be able to keep Reg's existence a secret, Shiggy comes up with a plan for Reg to pose as a homeless orphan who wants to become a delver and approach Jiruo. Luckily, it works out and Reg is officially taken in by the orphanage.

During the Orth's Resurrection Festival, Jiruo finds Riko sitting alone. He encourages her to participate in the festival, since it is in her mother's honor, and Lyza was fond of them. Riko asks what type of person Lyza was, admitting she can't remember her mother's face. Leader's description is unflattering, but he was clearly fond of Lyza. He asks about Riko's eyes, and she says she no longer has headaches, as long as she wears her glasses. Leader reveals that Riko's eyes aren't bad, she is suffering from the Curse of The Abyss and he tells her about her birth.

Jiruo later informs Riko that she now has permission to view Lyza's sealed letter at the Delver Guild HQ. He orders Reg to accompany her.

During the day of Riko's and Reg's departure, Reg then runs into Jiruo, who is patrolling and already knows that Riko is missing. Despite Reg's obvious nervousness at being caught, Jiuro lets him leave. When Riko and Reg made it to the 1st layer they find a letter from Jiruo in which he tells them that he new of theier plan and is going to pursue them after alittle headstart, which causes them to star hurrying towards the 2nd layer. Luckily, with the help of Hablog, they make it without running into Jiruo.

Since then, while Jiruo has not interacted directly with Riko or Reg, he has been shown on the surface trying to help Mio with curing Kiyui; aswell as talking with Ozen in the Seeker Camp.