Kyomu Senshi Miroku
Genres: Action, Fantasy, Sci-Fi, Supernatural
Type: OVA, Episodes: 6
Aired: Jan 10, 1989 to Nov 5, 1989
Source: Manga
Rating: R+ - Mild Nudity
Synopsis:
A psychic ninja fantasy suggesting that the assassins did not die out during the Sengoku era but burrowed under Japan, where they fought a new war against the alien occupants of a crashed spaceship that has lain undisturbed for several millennia. 

(Source: The Anime Encyclopedia)