Six months after my younger sister Rika and her husband moved into an apartment managed by my uncle, my older sister and Itsuki also moved next door. There was nothing dissatisfied with the life with the couple Itsuki, who is on good terms... Rika had a problem. It's the shadow of the opposite sex that my husband feels, the betrayal of my husband that I know because I've always been by his side. However, a strong stimulus awaits Rika to counteract her growing anxiety. The relationship between "husband and sister" that my brother-in-law told me... And Rika's body that has been embraced by her brother-in-law, and...