Yeah i thought it was weird when i read that toobut if we want to defend it we can say he needed to discharge and decided to do it regularly little by little and trained himself until his body just adapted
Even if she does admit that she likes him we actually haven't seen anything that indicates medaka likes her he blushed and gave the same reaction to all girls so far
I honestly prefer him actually being upset rather than it being just a öne chapter joke since when it's the way it is now there is a real impact on the story