this one exactly fits ur desc: https://www.mangago.me/read-manga/sankaku_twilight/
and these 2 kinda but both ml and mc have unrequited love for the same person (love rivals)
https://www.mangago.me/read-manga/nande_koigataki_ga_ki_ni_nannen/
https://www.mangago.me/read-manga/love_your_love_enemy/
