Koi Uta Unlock

Guitarist Kouhei is always fighting with his other band members due to wanting to go a different direction. Then while he's at a local music venue, he hears an incredible singing voice and falls in love at first "sound." He doesn't know who the voice belongs to or where it came from, but when X mysteriously appears, Kouhei unconsciously gets hard. He searches desperately to find him again, but his only clues were X's voice and a tattoo on his left arm. After several months with no luck, he runs into X by chance at the convenience store! Kouhei starts hitting on the man who introduces himself as "Rei," only to be completely rejected...

(Source: Dogenzaka Shobo, translated)

Note: Originally serialized under the title "Looking for a Treasure".