Bukiyou de Gomen

from -dokidoki- :
Ichirou's best friend Naoto's noticed that he's been acting a bit unusual since summer vacation. With a bit of best-friend solidarity, Naoto squeezes out the tale of Ichirou's secret summer fling: a sexual encounter with a mysterious stranger fleeing from a rainstorm. Naoto is, naturally, scandalized, but not half as scandalized when he and Ichirou run into the summer fling again at a school festival...

As if a guy falling in love with another guy wasn't complicated enough! How about when that boy's already got another guy after him? Throw a live-in cousin with an aggressive crush and the world's cutest lovestruck best friend into the mix and the situation gets rather convoluted, even by Koide-standards.