Omega wa Pink no Yume wo Miru
Complete | Sakurai nanako | 2000 released
So the romantic interest is drugged and raped by the protag and the protag is forgiven by saving the romantic interest from a rape by someone else. Let's also not forget the personality change in the romantic interest in chapter 4. Either the translations are off or this just isn't good.
Sakurada-senpai Kaizou Keikaku