Sarutobi was born the nephew of the famous hero of Yamagakure, Nagato Yorozuya. For this reason, he was chosen by Ryun Uchiha, the First Yamakage, to be the host of Yamagakure's newly acquired tailed beast — Saiken, the Six-Tails. According to witnesses, however, it was D, one of the elders of the village, that sealed the beast within the boy.