Not BL and incomplete (sorry):
http://www.mangago.zone/read-manga/koudaike_no_hitobito/
I LOVE THAT SERIES<3<3 I've loved Sensei ever since I read Gokusen! Gokusen is among my favourite series of ALL time! Have you seen the live action movie for Koudaike no Hitobito? If not, you should definitely try it! It's adorable, and Haruka Ayase's acting - she's an angel in that movie! Although she's always an angel, haha <3
I'm OK with BL and non-BL, too~
idk if this fits since he's kinda crazy since the beginning:
http://www.mangago.zone/read-manga/kare_no_satsujin_keikaku/
It's only chapter 0. idk why the other chapters are there
And I haven't read it in a while, but I think this tragic romance fits the bill, iirc:
http://www.mangago.zone/read-manga/paperweight_eye/
Any recommendations of mangas with really delusional characters? The type that just drift off into outrageous fantasies at the drop of a hat? I just suddenly started craving them...