In a dystopian Japan where the National Prosperity Law has become deeply entrenched, the government continues to administer the lethal inoculation known as the nano capsule to children in first grade. A small percentage of those capsules activate between the ages of eighteen and twenty-four, killing the recipient. Twenty-four hours before the death, a notification called an ikigami, or death notice, is delivered to the condemned person, supposedly to remind society of the preciousness of life. The sequel, Ikigami: Sairin, takes place after the events of the original series and shifts focus to a new protagonist, Yasunaga Kunihisa, a former thought criminal who was reeducated and now works as an ikigami delivery man at the Nishimoriyama Ward Office. After an administrative mistake, Yasunaga is forced to deliver an ikigami to his own estranged son, an event that triggers severe psychological stress and physical symptoms such as tremors and autonomic nervous system disorders. As he struggles with the weight of what he has done, he begins receiving recruitment messages from the anti-government organization he once belonged to, the National Prosperity Destruction Plan, causing his long-suppressed resistance consciousness to reawaken. The story expands the scope of the original by depicting a society under even tighter government surveillance and control, where the National Prosperity Law has grown more entrenched and the state has intensified its monitoring of citizens. Anti-government movements are rising in response, and Yasunaga is caught between his duty as a delivery man, his guilt over his son, and the pull of his former ideals. The narrative is structured around serialized episodes with titles such as The Stolen Life, The Implanted Conspiracy Theory, The Nation of Human Rights Violations, The Hidden Truth, and The Death of the Heart of National Prosperity, each focusing on different recipients of the ikigami and their final twenty-four hours, while also following Yasunaga's internal arc and the broader political conflict between the state and the resistance.