Jin Ashima (born 1994) is a novelist whose fiction combines ancient Chinese history with puzzle-driven mystery. He is from Hirakata, Osaka Prefecture, and graduated from the Faculty of Agriculture at Kindai University. In 2026 his manuscript “Suirojo no Seigai” won the grand prize in the sixteenth Agatha Christie Award. Retitled “Suirojo no Satsujin,” the novel is scheduled for publication by Hayakawa Publishing on November 18, 2026. It is set in 225 BCE in Daliang, the capital of Wei, as an attack by Qin floods the city. Within an isolated castle, the king is murdered in a locked room and an emblem of royal authority disappears. The seven survivors become suspects, while a Wei general investigates and further deaths follow. The story places a sequence of murders within the historical collapse of a state, using a castle surrounded by floodwaters as the setting for a closed-circle mystery.