Oshiete Boku no Kamisama

Kei and Mako have been friends since junior high. Mako was kind to everyone, so he was always surrounded by a crowd of fans. Kei had a crush on Mako, but he was content to stay by his side as a friend.

At the high school graduation ceremony, Kei finally confessed his feelings to Mako, only to find out that Mako felt the same way, too.
Kei was overjoyed, "We can finally be together!" But then Mako revealed his secret to Kei, that he is a "kami-sama."

(Source: mimosa, translated)