Boku no Pico

During summer vacation, Tamotsu is on break from work happens to visit a particular café. It is at this café that Tamotsu meets Pico, who works there for his grandfather. Tamotsu instantly falls for Pico, believing that Pico is a girl because of his feminine appearance. However, to his disbelief, Pico claims he actually is a guy. Undeterred, Tamotsu pursues a sexual relationship with Pico, to an extent where he even persuades Pico into wearing girl clothes. When Pico asks what is he to Tamotsu, he finds himself unable to answer...

(Source: MAL Rewrite)