History remembers kings, wars, and the people who changed the world. But what about those who were never meant to be remembered? Bon Namihira, Yumiko Yasukawa, Ream Stream, and Buyoyon continue their work as Time Patrol agents, rescuing ordinary people whose survival will not alter history. Their mission is simple: save lives, protect the timeline, and leave no trace behind.

But strange fractures begin appearing across history, all connected to Bon's past missions. A mysterious figure known as Hatuso Minami emerges—a human who should not exist. Haunted by the erasure of his family during a forgotten Time Patrol operation, he asks a devastating question: Who decides the value of a human life?

As secrets surrounding Case File 0 come to light, Bon must confront the hidden cost of protecting history and learn that sometimes the greatest act of heroism is simply caring about someone the world forgot.