Wasureta Koi no Shuufukuhou

Shoma Yagi is 18 years old. He's been harboring one-sided feelings for his childhood friend, Mizuki...or he was.

When Shoma wakes up, an adult Mizuki is standing right next to him. What's even more shocking, Mizuki claims that they're boyfriends?! To Shoma's surprise, he had lost all of his memories of the past 7 years. The Mizuki who stands before him now is mature, sexy, and nothing like the Mizuki in his memories. But to Shoma, the last thing he remembers is realizing that he had a crush on his childhood friend. The sudden change in their relationship may be too much for poor Shoma to handle...

(Source: Tokyopop)