It always caught my attention that everyone thinks it could be Matsu who raped Hiroko Or maybe someone else, but why couldn't it be Hiroko who actually raped him?
One night with an extra glass of wine, she climbed through the window while matsu was sleeping and took advantage of him, she was afraid of losing him and did that, but later felt bad about what she did since she raped him and thinking that If she told the mc the truth he would really get mad and lose him and since she never said anything to him in the end the mc just assumed she cheated on him. (we know that the wife does not tolerate alcohol and that she has had sex with the mc while he sleeps, it really would not seem strange to me if it turns out to be something like that haha, maybe I'm missing a key part so that wouldn't be possible, but it was so long ago that I played that I really don't remember the scenes of the past really well
)