Some time after the OAV was released, it was decided to make a Kakyuusei TV series. There are a few differences between the two series, and keep in mind that they are unrelated in their storyline. The OAV was only a 4 part series that mainly focused on Mizuho, Miko and Ai, while the TV series is a 14 part series that features almost all the girls. The main male character in the TV series is Tohru Nanase, while in the TV series it's Tsuyoshi Yamaguchi (more information here).

The TV series you could say is more true to the Kakyuusei game than the OAV. The story follows Tsuyoshi and his relationships (not necessarily romantic) with various girls through the four seasons. Through all this Tsuyoshi goes through good times and bad, and takes an interest in many girls, but in the end he'll only choose one.