Orokamono Wangel Night

When the guy Kira is dating takes all his money and runs off, Kira heads into the mountains, heartbroken and underdressed. On the verge of distress, he's rescued by Fuji, an unfriendly man with a frightening look in his eyes, and they end up sharing a tent for the night. But given an excuse, Fuji gropes Kira's ass and pulls down his pants?! They just met, and they're having wild sex?! One night of love in the mountains changes fate.

(Source: Taiyo Tosho, translated)