Is it illegal for two men to be in one of those sex hotel rooms?

Question:

I hear its illegal and its also illegal if 1 women and 2 guys go into one of those sex hotels in Japan.
they will arrest you on the spot.

Is it true?

Answer:

Many times in a love hotel you never see the owner and they never see you - it is all anonymous, and you pay a vending machine in the room to unlock the door for you when you want to leave.
So you can pretty much do what you want -- but if you ask if it is OK, most owners would frown on such activities - it can ruin their reputation and business if the place becomes infamous.