Nanbu was a simple budoka of Otosan Uchi, in the 2nd century. One night he led a group of peasants to save the life of Soshi Saibankan, who had been ambushed and his yojimbo slain. Nabu had always admired the magistrate, and the group became the personal guard of Saibankan. After raising his son in Saibankan's service, Nanbu finally died holding off a group of bandits while a messenger escaped to bring word of their location to Saibankan. Nanbu's son, named for his father, continued to serve Saibankan. Their descendants eventually would be granted by the Soshi as the Nanbuvassal family.