A crashed alien ship buried beneath feudal Japan turns ninja into something stranger than myth. Psychic assassins fighting extraterrestrial invaders in underground tunnels is the kind of premise that only works if you commit completely to it, and this OVA does. The show treats ancient bloodlines and alien warfare as the same historical fact, refuses to explain the contradiction, and moves on. You're either in on the conspiracy or you're not watching. Real 80s sci-fi energy that doesn't bother justifying why ninjas and aliens share the same underground empire for thousands of years.

Set in an alternate take on Japanese history, this psychic ninja fantasy imagines that the country's ninja assassins never vanished after the Sengoku era. Instead they went underground, beneath Japan itself. There they fight a new kind of war against the alien occupants of a spaceship that crashed long ago and sat undisturbed for thousands of years. The six-episode OVA mixes action with science fiction, setting ninja with psychic powers against extraterrestrial foes.