This is a perfect example of inaccurate translating leading to misinformation spreading.
Okay so in this video (around 3:50) Kai shows his business card that has ドMドラマー戒 written on it which means “Super Masochistic Drummer Kai”. Kai then proceeds to explain it like this:
“So about why I made it like this.. I don’t want you to misunderstand the “Super Masochist”. It’s about how I don’t want to forget the masochistic side of myself. I constantly punish and strongly criticize myself. That’s where the name “Kai” comes from (his name is the kanji from the verb 戒める which means to admonish, to punish, to warn, to forbid etc).”
So in this case by masochist he doesn’t mean a masochist. He means that he’s very, very strict with himself. Nothing to do with what he’s like in the bedroom.