Eleven-year-old Natsuru Nanao is the ace of the soccer team yet has trouble speaking to girls because of a certain event following his transfer to his current school. Due to his father dying long ago, he lives only with his mother but does not let this distract him from his passion for soccer, as he hopes to become a professional player. One day, a female classmate named Rio Suzumura approaches Natsuru, a meeting that signals a huge turning point in his life.

Upon talking with Rio, Natsuru immediately becomes interested in her. After he saves an abandoned cat, he runs into the girl and her younger brother, Yuuta, on their way to the supermarket and asks if they can take care of it, to which they agree. However, when Natsuru arrives at their home, he is shocked to discover that the siblings have been living alone in a dirty house, a secret that Rio absolutely wants to keep. As Natsuru spends more time with them, their circumstances and reasons for secrecy are slowly brought to light.