After his parents died, Shinjiro went to live with his older brother and his wife. His sister-in-law, Aki, is dissatisfied with her nighttime routine with her husband, Kotaro. The two of them open a forbidden door through an unexpected opportunity. She sees her brother-in-law asleep in his room, naked from the waist up, with a porn magazine in his hand. His rock-hard cock triggers Aki's desire...