It's a yaoi about a guy who makes a bet with his friends about getting his friend's younger brother. He manages to sleep with him multiple times until the younger over hears about the bet. There's also another story where the younger brother's brother has a sex friend who tries to be his number one. I forgot what its called. I think its by fujisaki kou, but I'm not sure. Thank you!

From 701 Goushitsu?