Crimson Pledge (2014)

A lady AKI and her boyfriend TOMOYA have a surprise-retirement party for his father TADASHI as a teacher. Aki plans to invite many of his students. However, some students start talking about their sexual contacts with Tadashi while drunk. In fact, this party was thrown by Aki for taking revenge against her father who left her when she was a child. While trying to find her roots, she knew Tadashi had many infidelities and also had relationships with his students. Tadashi loses his reputation completely but Aki regrets what she did. Overall, she decides to live alone with her baby.