Fujii Yakumo

A boy characterized by his slit eyes. On his way home from work, he meets the heroine, Sanjiyan (a three-eyed demon), named Pai, and becomes immortal to protect Sanjiyan, turning into "Wu". He embarks on a journey with Pai to become human. The age at which he became immortal is 16, a high school second-year student. As the story progresses, there are depictions of advancing times, but since he does not age after becoming immortal, there is no change in appearance.

He has a nature that dislikes fighting, and he tends not to take lives, even if they are enemies, often helping at his own risk. Especially against female-type monsters, his restraint is noticeable, and he often falls into a predicament being betrayed. He is good at cooking. "Give me a break" and "Yakui (meaning 'dangerous')" are his catchphrases. He seems to have a fear of heights, and he is not good at Chinese.