it's complicated biologically, they kind of come from the same demon (kimoto from the brain and jin from the heart), but kimoto was a parasite in the demon's brain and was put into a human boy's body, so he was technically never really from the demon, but he still was in a way LOL they'll probably take on a more familial/friendship dynamic in the story, but they're not related

I think Kimoto's current character arc sums up one of the main reasons I love this webtoon! Kimoto's actualization of his emotions is actually so stupidly profound, how his logicalization of his emotions is merely a front for his intense and selfish desire to be loved. Despite his efforts to distance himself from it, he is squishy and vulnerable and desires to connect in such a uniquely human way. And I think this kind of echoes the themes of the webtoon: the vulnerable and endearing humanity that shines among absurdity and mayhem.
BL got me philosophizing lol Don’t worry I definitely still remember the absolute experience that was insect sex :,O Stay freaky stay sane!