Aganju was the fifth Alaafin of Oyo, and son of Ajaka. His ascension to the throne was devoid of dramas, which would have probably been the case if he had a cousin from Sango, his uncle. Ajaka designed the palace innovatively as king, and he domesticated some wild animals. It is said that he tamed reptiles too, some of which may be seen crawling over his body. Aganju was responsible for erecting over 120 of Kobi, high thatched gables and porches underneath them. Only the palace of the Alafin in Old Oyo was allowed to have this kobi, which served as a place for the Alaafin to view people who greeted him in his courtyards without being fully exposed.
Aganju led a long and prosperous reign, save the crises that rid his throne towards the end of his life on account of a pretty woman he met. He waged war against the lord at a neighboring town, for refusing him the hand of his daughter in marriage. Princes and warriors died in the war. Aganju had also killed his supposed heir, Lugbe, after the later was found having intimate contacts with the new belle of his palace, Iyayun, daughter of the the Onisambo who he captured. The king was therefore overcome with grief and died not long after, months after Iyayun got pregnant of the child who is to become the sixth Alafin.