This was a series back in the Fakku days, the manga was part of a series.

Setting took place in a modern, Japanese high school setting. I think the main girl was blonde and knew how to fight. The main guy was a nerd who didn't know how to fight.

Don't remember much but the penultimate manga was the girl was caught and being raped in some sex dungeon that had leathered gimps. She manages to escape some how from her binds and the rapist instead rapes the main villainess girl.

Meanwhile the nerd MC is getting his ass handed to him in a fight at the highschool. The most distinct part I remember form this whole series is the nerd MC leaps from a high ground and aims his fist at the villains head but he misses and punches the concrete instead. Villain starts laughing his ass off, but the main girl arrives on time to kick his ass herself.

Happy ending is the nerd MC and the main girl get together and fuck.