"Three Days of Happiness" is a manga adaptation of the novel by Sugaru Miaki, illustrated by Shōichi Taguchi. The story centers on Kusunoki, a 20-year-old man disillusioned with life, who discovers he can sell his remaining lifespan for money. After visiting a mysterious shop, he learns his life is worth only 300,000 yen, a shockingly low amount reflecting his lack of meaningful relationships or accomplishments. The shopkeeper, an enigmatic figure, offers him a deal: he can sell his lifespan, time, or health, and in exchange, he will receive a small sum of money. Kusunoki chooses to sell all but the last three months of his life, leaving him with just 90 days to live.

As Kusunoki begins his final days, he meets Miyagi, a young woman assigned by the shop to monitor and document his remaining time. Initially indifferent to her presence, Kusunoki gradually forms a bond with Miyagi as they spend time together. Through their interactions, Kusunoki reflects on his past, his regrets, and the choices that led him to this point. The narrative explores themes of human connection, the value of life, and the search for meaning in seemingly insignificant moments.

The story is structured around Kusunoki’s journey to find purpose in his limited time. He reconnects with people from his past, including a childhood friend and a former classmate, but these encounters often highlight the emotional distance he has maintained throughout his life. As the days pass, Kusunoki’s perspective shifts, and he begins to appreciate the small joys and fleeting beauty of existence. Miyagi, too, undergoes her own transformation, revealing her own struggles and vulnerabilities, which deepen their relationship.

The manga’s tone is introspective and melancholic, with moments of warmth and humor. It delves into the complexities of human emotions, portraying Kusunoki’s gradual realization that even a life deemed worthless by others can hold profound significance. The artwork complements the narrative, capturing the subtle expressions and quiet moments that define the characters’ experiences. By the end of the story, Kusunoki’s journey culminates in a poignant exploration of what it means to live and die with purpose, leaving a lasting impression on both the characters and the reader.