You got transported to novel world as the bastard. The character who steals the Rina from Steven. Your character was supposed to be a playboy delinquent. But you decided to just avoid the stealing plot.

However, you unknowingly saved Rina from a group of guys. She heard about your delinquent rumors, but thanks you anyways. Soon she started to notice the you're not like the rumors. And started to catch feelings for you. That wasn't supposed to happen... In the novel, your character took her by forced. But now she's actively pursuing you. Now, Steven is glaring at you in class. Since the girl he loves, since childhood, is after you.

Rina: "Let me come over to make dinner for you as a thank you."