Honestly I wish he'd meet her half way...
This manga is a bit of an extreme case, but it's not unusual in a relationship to have different desires than the person you love (and I am talking about the physical side of a relationship, though it's true for other things too).
Even just on how comfortable one is about holding hands in public. Some people find even mild PDA extremely embarrassing, some will feel strongly that they are being rejected if they don't receive or can't give gestures of affection in public.
Even on how much sex people want, if someone has a high libido, that can be difficult and a burden to a person who's sexual needs aren't as high.
Like I said, this is an extreme case, but having to figure this stuff out is part of relationships. She's been learning this stuff to gain his affection which was about as unhealthy a way to start a relationship as can be. I mean as a result everytime they meet they do some sort of play because that's the only way she thinks she can keep him interested, it's about time they just had a friendly chat and a regular date. They really need to talk more about everything, she might be forcing herself a little bit, but lets be honest she's finding enjoyment in it as well, and there's a certain kind of empowerment in successfully pushing your limits (also why the hell is the guy with experience in this stuff letting her learn it all on her own? I guess he was pretending to be coerced until this chapter, but seriously with that kind of kink it's a recipe for disaster), and if he's that concerned about "corrupting" her then he can try a few regular things himself, he might not get the same satisfaction, but going out in an average way shouldn't be hard, they can always kink it up in private later.
Sorry for the rant. Just please, if you are in a relationship where your needs aren't being met, talk to your partner, tell them what you want. If that changes over time, tell them that too. It's normally not that difficult to find a compromise when you care about each other, but you both need to understand what the other needs and expects. If only one person panders to the other's desires... well that's a lot of suffering.