Elektel Delusion

Shunpei and Fumi are best friends and neighbours. One day, Fumi tells Shunpei he might be gay and has agreed to go out with another guy in school. Shocked at this sudden confession (but very accepting), Shunpei questions Fumi about all sorts of things regarding his newly-discovered homosexuality - subtly aware that he's disappointed that Fumi picked someone else over him - and, upon meeting the boyfriend, cannot take that Fumi chose someone who was more or less normal... like Shunpei!