Unsuccessful NTR/BSS type of plot. Either recommendation or find what I was looking for. H-manga

[fobus]

So I vaguely remember the story starts out showing girl A and guy A having sex. Then cuts to a school setting where guy A is plotting to target girl B for her body and planned for girl A to invite girl B to karaoke. MC likes girl B and is very aware of what kind of person guy A is and is plotting. Girl B fell in the trap and was drugged at the karaoke, but before guy A can make his move, the MC breaks in and attempts to stop him. MC was stalled by girl A by having "sex battle" while guy A was continuing taking off girl B's cloths and making her horny. At the last moment MC win in the "sex battle" against girl A and some how immobilized guy A. Then MC get to have sex with horny girl B and by the time girl A wakes up then they have threesome leaving guy A in defeat.