Bastard. Not THE MC, but one of the MCs.
Ayeshah's Secret. If not outright crazy then seriously fucked up in the head, at the very least.
Kare no Satsujin Keikaku. It's a oneshot, though. Maybe he's not, but idk, I'd qualify "I wanna murder coz it sounds interesting/fun" as batshit.
Miss Not-So-Sidekick. The ML is fucking insane, and it's sometimes acknowledged, but it's not really a "thing" like a think you're looking for.
The Way to Protect the Female Lead's Older Brother. So the ML isn't crazy and the FL managed to hang onto sanity by becoming completely ruthless and holding virtually no attachments. 90% of her family, which is heavily featured in the story, is fucking insane.
The Sound of Sugar Cubes. I really can't remember HOW insane one of the dudes is because some of it is lies, and I can't really remember how prevalent he was in the story.
ayeshas secret is jst, chefs kiss
hello, can i please get reccs where the mc is just batshit insane? bl, gl, or no romance is fine! no het or harem pls <3