In feudal Japan, a series of mysterious deaths plague a castle town's young samurai. The chief retainer investigates and uncovers a shocking truth: a beautiful princess named Tsukihime is secretly infecting them each night. With the help of a monk's magic, the retainer traps Tsukihime and sinks her into a pond. However, a female ninja servant's attempt to rescue her triggers a massive earthquake, sending the princess and the ninja forward in time. They arrive in a modern world grappling with the emergence of AIDS. Their appearance causes widespread disruption as employees at a company begin collapsing.