I don't remember exactly what it was like, but there was a manga I think about cannibalism (it's not Tokyo Ghoul). Probably a one shot or a volume, where there was the protagonist, and I think, but I'm not sure, his sister or someone he knew. It seems like he had some experiment being done by someone, which was slowly turning them into monsters.
In the end one ate the other, something like that, but I'm not sure about that ending.

Does anyone have an idea what it is? I would guess it was back in 2018 when I read it, but I'm not sure either.