Struggling financially and helpless, Kusunoki is forced to sell his belongings to buy food. A kind shopkeeper, recognizing his poverty, sends him to a store that claims to buy lifespan, time, and health. Though skeptical, Kusunoki visits out of desperation and curiosity.
The bleak reality of his lifespan's monetary worth leaves Kusunoki devastated; he is offered a mere three hundred thousand yen. In his desperation, he decides to sell the next 30 years of his life for ten thousand yen per year, leaving him with only three months to live. Upon returning home with the money, he is greeted by a surprising visitor, the same clerk he sold his lifespan to. She introduces herself as Miyagi and is tasked with observing him until his final three days.
The remaining three months of Kusunoki's life are chronicled in "Jumyou wo Kaitotte Moratta. Ichinen ni Tsuki, Ichimanen de." as he confronts past regrets and discovers what truly makes life worthwhile.