Based on a PC game released by Tactic in 1998. The game was very popular and it was dominating that particular (romance-drama-eechi) game genre in Japan that year. It was so popular that there were several Drama CDs released, and finally the OVA about two years later.
The main character of the story is Orihara Kouhei, a mysterious boy with a tragic past and tormented by memory loss in his childhood. He had disappeared for a long time, then returns to fullfil the promises he made to several girls in his past which he have forgotten.