Nin x Nin: Ninja Hattori-kun, the Movie

Kanzo Hattori, an apprentice Ninja, leaves his home town of Iga for his final training. He must go to the city of Edo (Tokyo), and the first person he meets shall be his master, whom he must protect with his life, whilst upholding the ninja code. Also while in Edo, Hattori must find out why their rivals, the Koga Ninjas, are flourishing while the Iga Ninjas are dying out. Hattori's master is Kenichi, a 9 year old boy. (imdb)