Umm actually he did rape Jae Oh. I forget what chapter specifically. It was during the time where Seong Rok still in that woman (forget her name) manipulation. I guess it was in the scene when Jae & Seong went into rural place to find a man that will be accused as the murder by police. Jae Oh giving attitude because he was mad at Seong Rok, then Seong Rok forced him into submission through rape in the car. It was during their early relationship before they build a bond like they're now. So the author didn't really make rape happen out of the blue. It was something ever happened between them and Seong Rok has the ability to do it as he ever did before.
im genuinely upset abt the rape part cuz this manhwa was literally so fucking good, i was happy that we had a psychological and dark manhwa w no rape but bruh the author had to ruin it