Owls' Castle

"Owls' Castle" (2000) is a Japanese movie about ninja. It is a remake of 1963's "Castle of Owls," which was based on a novel by the same name. In it, a powerful warlord wipes out a ninja clan. Years later, one of the survivors hires an assassin to avenge those deaths. That assassin has the job of sneaking into Japan's most heavily guarded castle and killing the country's ruler.