Well that adds some clarity, I don't recall it being mentioned in game that ALL 3 girls studied martial arts, I even don't care if it wasn't mentioned that's good enough reason.
My previous comments were geared more towards if MC had to prevent bodily harm to his person from Mel/Alice, a pure strength benchmark between man & a woman who are in similar physical shape, typically the male would be stronger in logical way, BUT this is all moot as mc is a beach bum And all the girls are apparently martial artists >;D
(I was trying to save some face For our MC, but let's admit he's honorless, lmfao)