Review Detail of Cestarian in Battle Royale of the Sinners

It was an ok self insert, until the protagonist did a 180 after claiming he didn't want to be a harem protagonist, and sticks his dick in a disgusting cannibal girl, cheating on the girl he's supposedly in love with. For a fucking disgusting cannibal... Yeah I don't even fucking understand anymore, it's like the author just couldn't keep it in his pants all of a sudden, we already had a romance subplot going on, and the author just straight up ruins it out of the blue after previously committing to not doing so :|