During her formative years, Nikaido Aki was exclusively familiar with Mahjong. Her parents managed a Mahjong shop where Aki, her older sister Rumi, and their family would convene for leisure. However, when their mother suddenly departs, their father is compelled to shut the store down, leaving Aki and Rumi in the care of relatives. Without a clear direction in life and uncertain if she should pursue high school, Aki must define her aspirations.