I agree with Kaitensatsuma he doesn't keep the trauma, which I thought when he was being flustered by her. She even sayed I'll make you fall in love with me and then part ways with you.I
That alone should have reinforced his trauma of distrusting Senseis\teachers but noooo he is still flustered her.
They should have made him question the confession. When she revealed her breasts and played on the table with her legs spread, he could have been aroused but thinking she was trying to set him up by saying he forced himself on her.
The jokes could come from her confessing and trying to get him to call for her but him turning her down. The situations seemingly looking as though she is/might be setting him up. He could even call out the situations 1\3 to 1\2 the time.
@Kaitensatsuma you are right, he should have been a normal ordinary guy. It certainly looks like they are going to drop that trauma thing.