Can someone tell me what manga is this?

The two is not actually a couple, they're more like sex friends (one guy is tall and serious then the other one is short and always smiling). Then there's another guy who's in love with the short one. The short one can't choose between the two and since the third guy is so in love with him, he agreed to live with them. While living together, the third guy and the tall guy start to feel something for each other. The short guy noticed it so he told them that they can only have sex twice or thrice (not sure) if he's not there. :) thanks..thanks