OMFG...yea I know. That totally came out as a "wtf" moment. But I was talking about the anime. He basically shows her all his erotic games and figurines in an effort to driver her away, but Nanako responds with "I think ecchi games are gross, but the way in which you're so open about it, that's what I like about you". Yakamoto didn't expect this, so he says something about her being into tentacle rape. Then she punches him and leaves. Yamamoto only wanted to driver her away because he was leaving Tokyo forever and there was no way they'd be able to pursue a relationship. And the end of the episode with the black screen you can hear him say "sayonara, Nanako-san". That part was really quite emotional for me.