Iruka Umino is a very important character in Naruto. He is an instructor of the Ninja Academy and the first person to have ever shown any compassion towards Naruto.
When the Nine-tails Fox attacked his village, his parents were killed, leaving him orphaned at a young age. He would often be comforted by the Third Hokage and Mizuki, even though Mizuki did this to try and hurt Iruka.
Iruka was then assigned to teach at the ninja academy where Naruto was a student. Iruka looked after him and although he reprimanded him and berated him many times, he actually showed that he cared about Naruto a lot. He would treat Naruto to ramen in a lovely little ramen shop run by a few other people who showed very little hostility towards Naruto.
At one point, Mizuki tricked Naruto into stealing a sacred scroll. Iruka caught him with the scroll and found out that he was set up. A little afterwards, Mizuki revealed to Naruto that the reason why the villagers reviled him was because he had the Nine-tails demon living inside him, the very thing that all of the villagers were forbidden from ever doing. This shocked Naruto to the point where he almost lost his mind. However, Iruka then showed how much he cared about him when Mizuki tried to kill him with a large shuriken. Iruka stepped in front of the shuriken and took a blow to the back. Although it was very painful, it didn't penetrate him enough to kill him. He then expressed to Mizuki that he never reviled Naruto for containing the demon within him and always thought of him as a member of the Hidden Leaf. This touched Naruto greatly and from then on, he was able to demonstrate his full power and continued to train to be the Hokage that he dreamed of being.
Ultimate Story[]
Iruka made his first appearance in Ultimate Story 3. When his world was overtaken by Darkness, he bare witnessed Naruto and his friends revert to being young children. He also became shocked by how much the villagers still hated Naruto despite all that he did for them. From then on, Iruka dedicated himself to looking after Naruto despite all the backlash that he received.
When the Woofoo Alliance first arrived at their world, Iruka along with the other adult shinobi made a request to them to retrieve Naruto and his friends so that they can find a safe place to protect them. They did just that before they were able to find a way to leave their world. However, they did make a promise to them that they will return to save them from the Darkness that had completely taken over their world. From there, Iruka and the other adult shinobi stashed Naruto and his friends away someplace safe and awaited the return of the Woofoo Alliance.