Umi to Futari no Enbun Noudo

Ryuuta has worked a summer job in Naoki's pub for several years, falling deeper and deeper in love with him despite Naoki's long-term girlfriend. But as soon as Ryuuta decides this will be his final summer on the job, he finds out Naoki's girlfriend is gone, and Ryuuta can no longer resist telling Nao-san about his feelings.

(Source: MU)