Just started reading this.
Ch 4- the doctor is giving
As for the MC's relationship with the girl, I do think both of them were in the wrong, he should have communicated with her about his problem (while it is a private matter, I still think he could have told her something and not just ignored her) and as for the girlfriend, if she has such a kink, you should always give your partner a heads up and not just suddenly start doing it, while not even confirming if they're comfortable with it or not, respecting your partners' boundaries is important in my opinion...
Weird but sooo cool