Responses
I think the translation was just messed up, I'm guessing what it actually said was along the lines of "after my mom had remarried I was feeling lonely and I accepted to go out with my girlfriend a day when she wasn't home." I'm assuming mother was on honeymoon and he felt very lonely so he accepted the confession. (That's what years of deciphering butchered translation experience is telling me but I could be way off)
Can someone explain more about the girlfriend situation pls. Did he do it with her already? Also, why they showed the mom when he was talking about the girlfriend. It was a bit confusing( ￣□￣||)