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)
Watch Kyomu Senshi MIROKU episode 1 online — subbed and dubbed, with automatic AniList / MyAnimeList progress sync.