Ienzo

Ienzo 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.

Kingdom Hearts Birth by Sleep
A young boy who speaks little--but his serene gaze suggests he sees much.

Even and the others at the castle are raising him since he has lost his parents.

Kingdom Hearts Birth by Sleep
Ienzo appears in Kingdom Hearts Birth by Sleep as a minor character with no speaking lines. His parents passed away for an unknown reason. 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 take care of him since the death of his parents, gives Ventus the directions to the Castle Garden where he would find Terra, and returns to the castle with Ienzo.

Blank Points
As Braig is interrogating Xehanort on his state of mind, Ienzo and Ansem walk past, eating sea-salt ice cream. The pair stop and turn to see Braig and Xehanort walking away, still deep in conversation.

Between Kingdom Hearts Birth by Sleep and Kingdom Hearts 358/2 Days
Ienzo was still one of six apprentices of Ansem the Wise, the ruler and scientist of Radiant Garden, alongside Braig, Dilan, Even, Aeleus, and Xehanort. Worried the Darkness in people's hearts would eventually consume his world, Ansem began performing tests on Xehanort's heart. Eventually, at Ienzo's persuasive influence, he created a laboratory in his castle's basement for such experimentation.

However, Ienzo and the other apprentices had their own intentions for the laboratory, and began conducting inhumane experiments on the human heart and the darkness within it. Such experimentation led to the mass production of the Heartless. Ansem quickly discovered their secret experiments, and immediately ordered them to stop. One day, after being advised to review their research data by King Mickey, Ansem found that the effects of their experiments had become irreversible. The apprentices then banished Ansem the Wise to the Realm of Darkness

Eventually, Ienzo and the other five apprentices dabbled too deeply into darkness through their continued experiments. Ienzo, along with the others, was consumed by the darkness, producing a Heartless. However, the apprentices all had strong wills, and so Ienzo became a Nobody ultimately named Zexion. The six Nobodies formed Organization XIII.

Appearance
Like his fellow apprentice Even, Ienzo has a scientist's appearance, wearing the same white coat that Even wears over a black, V-neck top with a white collar. Oddly, Ienzo appears to be much younger than his Nobody, Zexion, perhaps even younger than Ventus, making him the youngest of the apprentices. This may be due to the ten year gap between the two games' timelines. Otherwise, he completely resembles his Nobody, Zexion, with a few minor changes such as shorter, lighter hair. His eyes also appear to be a lighter shade of blue. Likely due to his size, Ienzo folds the sleeves of his lab coat back, and even then his hands are partially covered. He also wears blue pants and navy blue shoes, as opposed to the other apprentices' black boots.

Notes and References
Ienzo