Ienzo appears in Kingdom Hearts Birth by Sleep as a minor character with no speaking lines. His parents passed away for an unknown reason, given a home by Ansem in his castle and becoming the youngest of his apprentices. Disobeying the orders of his master to stay inside the castle, Ienzo was ultimately surrounded and attacked by Unversed until Ventus comes to his rescue.
Shortly after the battle, his escort Even arrives and gives Ventus both his and Ienzo's thanks, explains Ienzo's past and that he had been assigned to look after the boy, giving Ventus the directions to the Castle Garden where he would find Terra before taking Ienzo back to the Ienzoienzo was one of the six apprentices of Ansem the Wise who made his debut in Kingdom Hearts Birth by Sleep and Kingdom Hearts Birth by Sleep Final Mix. Ienzo is the original persona of Zexion; his existence continued on as Zexion after his fellow apprentice, Xehanort, led him to his gradual descent into darkness. Ienzo is also mentioned in the Secret Ansem Reports found in Kingdom Hearts II