This is one weird manga, for sure. It's no wonder why they say there's manga about every subject in Japan. I don't even know what the subject is in this manga.
She's literally tricking him to do things by crying and guilt tripping him. A fetish should at least be harmless, but this is just peak degeneracy, and she's definitely not a normal kid either.
If you flip the genders, this becomes really fucked up, but I think that's supposed to be why it's comedic? It's like jokes about a train crash, it's horrible but you laugh anyways, but instead of "haha" funny this is "nervous laughter"