Shortly after the Kyūbi’s attack and the loss of his parents, Iruka became the village’s notorious troublemaker, drawing the attention of everyone, including the Hokage and the ANBU Hound.
While fleeing from one of his pranks, he ends up encountering Orochimaru, who kidnaps him and uses him as a test subject in one of his experiments. Although the Sandaime had already developed a certain fondness for Iruka, due to his position, pressure from the council, and the fact that Iruka was just one of many orphans from the attack, his disappearance was treated as a runaway from the village.
Due to the trauma, he ends up losing his memory. He becomes a snake-human hybrid.
He eventually becomes cold-blooded, needing to use chakra to keep himself warm. When he was young, his chakra control wasn’t very good, so he had to wear thicker clothes to stay warm.
