Watch Online Free on Watchseries. Ninja Assassin follows Raizo, one of the deadliest assassins in the world. Taken from the streets as a child, he was transformed into a trained killer by the Ozunu Clan, a secret society whose very existence is considered a myth. But haunted by the merciless execution of his friend by the Clan, Raizo breaks free from them and vanishes. Now he waits, preparing to exact his revenge.