Responses
The way your description triggered a memory in my brain like a sleeper agent
https://www.mangago.me/read-manga/love_history_caused_by_willful_negligence/
Oops wrong reply
not sure if it's shounen ai or yaoi but its about an uke who got asked by his friend (a girl) to seduce and later dumped the playboy seme. I think the uke is sick and his friend, the girl is somewhat ugly or something wherein shes made fun by everyone. Thats why uke agreed to take revenge for the sake of his friend