Yamato's love for his younger sibling is boundless. In his perspective, she embodies both cuteness and kindness, and nothing less is acceptable. However, the monotony of daily life and the intricacies of the world outside disrupt his idealistic hopes, revealing just how hard it is. Join Yamato, the steadfast older brother, and Masaki, the lovable little sister, as they bravely face and confront the unforeseen obstacles that arise in the daily lives of a typical family.