this message may be
offensive
@Anti-NTR_Agent NTR doujin: kimi no namida no riyuu o ore wa mada shiranai.
Plot: Mc is a soccer player in training, has a female friend he likes, bastard has eyes on female friend, proceeds to steal her and have sex with her, Mc finds out and heart broken and proceed to cry outside the track in the middle of the rain. (Try to read the doujin first to understand if you have time)
Story idea: takes place literally at the end, when mc is crying in the rain, a mysterious stranger holding an umbrella approach him and ask him what wrong. Mc explain what happened, stranger proceed to tell mc to don't let it those two horrible people get to him and focus what he was doing before all this. Mc told stranger that he was practicing for a soccer game to which caught the stranger attention. Stranger gives mc a motivational speech about soccer and gives him advice, to which the mc feels better and now has a new goal, and that goal is to be the best soccer player all over japan. Stranger wish him luck and leaves but mc ask him who is he, to which the stranger moves his umbrella and reveal himself to be none other than Yoichi Isagi (from blue lock) to which shocks the mc realized that he's talking to the number 1 soccer player in the world. Mc make yoich promises to watch his upcoming soccer game in a couple of months so he can prove he too can achieve his goal to which yoichi acceptes. (In this story you can make yoichi has already achieve his dream on being a world famous soccer player)
There that's my idea , if you want you can still make the mc get his revenge by exposing the bastard and his female friend in front of everyone after he win his soccer game.