Koi no Chishiryou

He'll never forget him—his ex-classmate Yuu, that is. College student Ryousuke was absolutely devastated when Yuu confessed his feelings and then promptly disappeared from his life without waiting for a reply. After desperately searching for years, Ryousuke is overjoyed when they suddenly meet by chance. His happiness is soon eclipsed by the fact that Yuu walks off into the arms of another man...

(Source: Yen Press)

Note: Includes a bonus chapter.