Reina and her husband Koji inherited their family home from their late parents, and although it was ordinary, they lived a peaceful life together. One day, her husband's younger brother, Shigeki, suddenly returns home. He tells her that he lost his job and has returned to rely on Koji, his only surviving relative. As the three of them start living together, Shigeki gradually begins to direct his sexual desires towards Reina. Reina is confused, but falls into a pleasure she has never experienced before. And then...