Winning the fight is irrelevant to the point you are making. The sex scenes occur during the fight while Arihama is still much stronger than the player. All you have done is make him extremely horny, while he is stronger than you. It would be very out of character for him to be submissive at this stage. At the end of the fight, yes it would be in character for you to be dominate with him but you don't have the time to have sex before he gets back up.