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