Boku no Shotaiken  

My First Time, ボクの初体験

Feeling down because the person he likes doesn't feel the same way back, Eitaro tries to take his own life. However, he is found unconscious and his consciousness is transferred into a young girl's body. As a girl, Eitaro learns that the girl he loves did indeed care for him, so they try to make their relationship work despite the challenges of Eitaro being in a female body.