Popular author Nya no Esa × Fitch's super popular work with over 270,000 copies sold is now live-action starring Konatsu Kashiwagi!

Tatsuya visits his girlfriend's family home to report their marriage. There, he reunites with Kōka, the little sister he used to take care of when she was young. Unlike her innocent childhood self, Kōka has now fully grown into an attractive adult woman.

That night, while the two were drinking, his girlfriend Yuba falls asleep early. Seeing this, Kōka begins seducing Tatsuya right next to her sister. Tatsuya's rationality wavers as he gives in to temptation and has a physical relationship with her despite the guilt...