The world as seen through a cat's eyes is restricted to the colors blue, yellow, black, and white. Because of this limitation, the feline Hachi finds life monotonous and remains apathetic at school. In class, his attention constantly wanders, but a new transfer student may be able to disrupt his tranquil world. Amid a student body composed entirely of furry animals, the lizard Aoi appears fresh and interesting to everyone. He is intelligent, polite, and dresses warmly even in summer. Despite the arrival of the new student, Hachi initially remains unmoved. However, a chance encounter soon leads Hachi to discover Aoi's secret: his tail emits a completely different shade—a color Hachi has never seen before. As he watches Aoi's brightly shimmering skin, Hachi is filled with awe and longs to witness this hidden spectacle again. The two share their personal wishes, and soon Hachi's monochromatic blue life transforms into a vivid blue.