Premise: The Mitsubishi J8M "Shūsui" (Japanese: 三菱 J8M 秋水, literally "Autumn Water", used as a poetic term meaning "Sharp Sword" deriving from the swishing sound of a sword) was a Japanese World War II rocket-powered interceptor aircraft closely based on the German Messerschmitt Me 163 "Komet".
Hypothesis: The Mitsubishi J8M "Shūsui"was never to be used after the World War II