One day, Yutaro, who lives alone, meets a married woman, Ai, at a nearby pub. He had a rift with his girlfriend's husband and was at a loss, so he decided to have a drink with her, but... After that, he became friends with her, and before he knew it, he began to have a physical relationship with her. Yutaro gave Ai a duplicate key to his girlfriend's house, and when her husband left for work, Ai started heading to Yutaro's house with her shopping bag in hand. Then, as if to relieve the loneliness of being a married couple, she begins to spend a lot of time in his younger boyfriend's room...