Geki Totsu The Insanity of Emperor Iemitsu (1989)

An order is given to the young shogun heir Tachehiyo to participate in an initiation ritual in Edo that will mark his descent into manhood and his ascension to the Shogunate. Unfortunately, the current Shogun has some serious inferiority complexes as well as a fairly strong case of being totally insane. At the direction of his vassal, he tasks Iba Shoemon (Sonny Chiba) to assassinate his eldest son and prevent him from ever reaching Edo alive, thereby ensuring the Shogunate will transfer to his favorite younger son. Fortunately for the young heir, seven samurai have been tasked with keeping the young master safe during his trouble, led by master swordsman Igo Gyobu (Ken Ogata). The odds are not good for their survival, but an oath is an oath