This one kind of has that vibe but its been a while this manhua updated
https://www.mangago.me/read-manga/ancedotes_with_master_after_the_novel_transmigration/
Kinda?
https://www.mangago.me/read-manga/void_zariya_ranmaru/ ml thinks mc likes ml's bro (noncon)
https://www.mangago.me/read-manga/hatsukoi_encounter/ thinks mc likes a girl
https://www.mangago.me/read-manga/shitsuren_junky/ Ig? Ml thinks mc only likes straight guys who are not him (ml pretends to be straight bc mc only goes for straights. Mc has only ever liked ml)
https://www.mangago.me/read-manga/u_don_t_know_me/ ml saw condoms and thought mc messed around even tho it was for them (dubcon? Noncon ig)
Thanks
when the ml finds out the mc is in love with someone and they aren't aware that it's them and then they would start hating on a nonexistent rival. it doesn't have to be the main plot point, I'll take it as long as it occurs in the story. I can't remember this happening to the mc, but if y'all have some those are also welcome too.