Tsugaru
Tsugaru is Aya's assistant and a half-demon caught between two worlds. He's best known for his work as an "Oni Hunter" at a traveling freak show before joining up with Aya, though these days he's more focused on keeping his demon side in check than actually hunting them.
He's got that typical aloof vibe—calls Aya his master, keeps things pretty formal between them, though they do trade jokes now and then. Despite the distance, there's an easy rapport there. Combat-wise, he's genuinely skilled, which comes in handy given what he is.
The real tension with Tsugaru is that he's slowly turning into a full demon, and nobody wants that. His solution? He regularly drinks Aya's saliva to slow the transformation. It's an unusual arrangement, but it works—Aya's immortality seems to have some stabilizing effect on his demonic nature. It's the kind of thing that keeps him tethered to humanity, at least for now.
Content compiled by AnimeList.moe from publicly available sources.
