Tsuma, Shougakusei ni Naru. / Если бы моя жена стала младшеклассницей

The moments Keisuke Niijima shared with his wife, Takae, were the happiest in his life. After their first meeting as coworkers, the bond between them gradually became stronger. They eventually married and were blessed with a daughter named Mai soon after. However, following Takae's death, time seems to have stopped for Keisuke, resulting in his inability to build a proper relationship with his daughter.

Ten years later, the gloomy Niijima household is bound for change when a little girl knocks at the door—claiming to be Takae's reincarnation. After confirming her identity, Keisuke's world brightens once more as he revels at the thought of making new memories with his beloved family. Unfortunately, this fortuitous miracle comes with its obvious drawbacks, and one mistake will spell more tragic consequences for Keisuke and everyone else involved.