The grandiose delusions of 20-year-old university student Kusunoki are shattered when he learns that his future will be miserable. Having to sell his personal items to make ends meet, Kusonoki is offered the chance to sell his lifespan to earn some money. But it is revealed he could part ways with his remaining 30 years of life at a paltry rate—which means that he will never find happiness in this life. Rather than endure misery, Kusonoki decides to sell his life expectancy, leaving him with three months to live.

Feeling liberated from social norms, he sets a series of goals for himself, one of which is to clarify his feelings for his childhood friend Himeno. Meanwhile, Miyagi, the clerk who bought his lifespan, is sent to monitor his activities in the case that Kusunoki may exhibit anti-social behavior. Although annoyed by Miyagi's constant presence, Kusunoki will do everything he can to find a purpose to his existence in the remaining time that he has left.