Wall of text. Feel free to skip it if you don't feel like reading.
Now, a lot of people feel like Hanako's sex scene was a real dick move on Hisao's part, but you have to look at it objectively.
In literally every single scenario, within five minutes of the girl taking off her shirt they were *******.
In Lilly's she says she loves Hisao, then 5 minutes later she's all "**** me now Hisao."
In Emi's she's like "**** wheelchairs. Also, my shirt just came off. **** me Hisao."
In Rin's he walks in and she's already almost naked and she's just all "**** I need an orgasm right now."
Then in Shizune's, within 5 minutes of their first kiss she's tied him to a chair and is riding him like crazy.
So, really, he has a lot of alternate universe precedent for the way he acted, and you really wouldn't think it's a dick move at all if she hadn't said anything in the last scene.
Just my two cents.