The Naito household consists of parents, eldest son Ryuichi, elder daughter Mizuki, youngest son Tomoya, and their senile grandfather. One day, five family members are simultaneously struck by an unexplained disease and given exactly one month to live. The grandfather alone is unaffected. Reeling from the prognosis, the family gathers at the dinner table for the first time in years, each person silently contemplating how to spend their final days. Ryuichi, an ordinary high school student, observes the strained silence that has long defined their home. It is Tomoya, the withdrawn youngest brother who has been a shut‑in for some time, who breaks the quiet. He announces that he knows exactly what he wants to do: take revenge on the classmate who bullied him into hiding. The revelation shocks everyone. Ryuichi is the first to step forward, offering to help his brother carry out the plan. The parents initially object, and Mizuki remains indifferent, but the decision has been made. The revenge is directed at a boy named Tashima, whose relentless harassment drove Tomoya out of school and into isolation. Ryuichi and Tomoya secretly plan a violent act, and on the appointed day they corner Tashima and execute it without hesitation. The deed is done, and though it succeeds, the family soon senses that something else is watching them—an unknown car parked outside suggests their troubles may not end with a single act of vengeance. Through the shared crime, the fragmented Naito family begins to piece itself back together. The father, who lost his job earlier and had drifted apart from everyone, the mother, who had been aware of Tomoya’s bullying but was sworn to secrecy, and Mizuki, who had always kept her distance, all become drawn into the consequences. The boundaries between right and wrong blur as the remaining time ticks down, forcing each member to confront what they truly value. The story unfolds across two completed volumes, following the family from the diagnosis through the planning and execution of the revenge, and into the unsettling days that follow—where the act of retribution may have reopened a door to further danger.