From Shinmakoku Scanlations :

"Want to try out a man's body?"

Kakeru, a socially awkward exchange student. Yuudai, who is always the center of attention. And Ryou, Yuudai's childhood friend. Under other circumstances, these three would never have gotten along, but before they knew it, they'd become a group of best friends.

However, when Ryou starts dating a girl, Kakeru finds out that Yuudai harbors feelings for Ryou. Kakeru, who has a secret crush on Yuudai, takes this as a chance to suggest the two become fuck buddies, so that he can teach Yuudai "how men love each other"...

The consequences of this lie soon start to haunt Kakeru.