Yonosuke Asagi is an inhabitant and de facto leader of the colony of Battleship Island.
Yonosuke is a brave and kind man. He once lost a leg while rescuing Yae's father when they were out on a journey. Even in Kenichi's journal he states that Yonosuke is the bravest man he ever knew; sacrificing his leg for the latter. He is also a great leader and has lead the people of Battleship Island, giving them hope for a brighter future despite the disparity of their situation.
Yonosuke has messy light brown hair. He also has a goatee beard. He wears a black coat on top of a white vest. In addition to that he has black pants and a pair of gloves. He also uses a cane that resembles the sheathe of a sword. Yonosuke, in saving his good friend's life, lost his right leg, replaced by a wooden peg.