One day, Saji, a college student living alone, meets Aina, a housewife, at a nearby pub. Then, the two meet by chance, hit it off, and end up drinking until morning at Zuo Ci's home. Although the relationship between a student and a married woman is not allowed, the relationship between the two deepens. When Saji gave her the duplicate key, Aina started going to Saji's house with her shopping bag in hand when her husband went to work. And she spends a lot of time with him, trying to relieve her loneliness of not being seen by her husband...