Love Square(2005)

Miki has a good job and works in an office. She's been dating Ryosuke and they're happy together... except for the fact that Miki is also in a relationship with her college professor Tanaka. Tanaka is trying to break up with Miki because of his wife, but Miki won't hear of it. Ryosuke is also unfaithful, and he has a one-night stand with Chihiro, who also has a boyfriend. The plot thickens when both girls discover they are pregnant, and don't know who to name as father. This romantic drama about relationships is proof that love can also come in squares.