There is a limit to the number of times the heart can beat during a lifetime. The Kokuhaku disease, which is a rare ailment, diminishes the strength of the heart and reduces the normal lifespan, leaving the sufferer with fewer heartbeats. The remaining heartbeats can be calculated accurately with the use of a specialized tool.
While Hatsu Takagi was changing her clothing, Hato Iijima accidentally sees the device attached to her chest. Hatsu chooses to lead a solitary and uneventful life to prevent any increase in her heart rate. However, she wishes to encounter every moment of her life with genuine passion and vibrancy. Recognizing her desire, Hato pledges to assist her in living her life to the full and experiencing a thrilling surge in her heartbeats.
