My husband has a younger sister... Spoiled since childhood, she's always given in to her older brother's wishes. But now, her presence begins to negatively affect my marriage. When my sister-in-law "Rena" moves to Tokyo for college and starts living with us, an illicit relationship develops between the two sisters-in-law. The beautiful wife "Nana's" heart can never return to how it was before. Their passion entwines, driving them into a relationship no one can stop.