The Time Traveling Virgin.

Shota bumps into Taizo, an old classmate, and is invited to his house. Once there, he is shocked to learn that Reiko, the girl he used to pine for, is now married to Taizo. Later that evening, Shota accidentally falls down a stairs while pleasuring himself sniffing Reiko's panties. When he comes to, he realizes that the fall has transported him 20 years into the past. Will Shota be able to change time and get together with his dream girl?