Misaki and her husband have been married for seven years, with her husband being 20 years older than her. Even though he has turned 50 this year, he is still infatuated with Misaki's body. Despite wanting it to be so, due to his old age, Misaki's husband quickly 'surrenders' even though she has not reached climax. The two also promised to always be honest with each other no matter what, and she kept that promise until one day... Hayato used to be a neighbor of her husband when they were young. Because Misaki's husband is much older, they always treated each other like siblings. Hayato often comes over to eat at Misaki's house three times a week. However, Hayato's true intention is not just to have a meal with his 'big brother'. He has always had feelings for Misaki, but she never noticed. One day, when she casually asked Hayato if he had a girlfriend, he gathered up the courage to confess to her. Misaki thought he was joking and tried to brush it off. A few days later, when he came to pick up some documents from Misaki, Hayato unexpectedly attacked her. Despite Misaki resisting, Hayato realized that she was actually enjoying it. And just as he thought, this was the first time Misaki lied to her husband. If she told the truth, everything with Hayato would end, but for some reason, she couldn't do it. So she continued to let Hayato have his way with her, and even actively sought him out. Misaki's husband had his suspicions, but because she kept lying, and because he trusted her too much, the two 'unfaithful couple' continued to have an affair right under his nose...