H.E.R.O.S KAI, which stands for Heavenhold Emergency Recovery Operating System, is an android designed to recover the systems of Heavenhold in the event of an emergency.
When Heavenhold was built, to be prepared in case control fell into the hands of the enemy, an AI that would support the Hero in regaining control no matter the situation began to be designed. Designing an AI that could discern Heroes as well as handle all the controls of Heavenhold turned out to be rather a challenge, so, the solution was to create an AI based on the mind of Kaden, who was best suited to carry out the mission. In the process of implanting Kaden's memories into the AI, however, the memories beginning from the time of Heavenhold's construction caused an error, leaving only the memories of Kaden's childhood intact. That is how the AI came to be code-named Kaden Artificial Intelligence, or KAI.
As a child, Kaden was overly enthusiastic and often shouted the word "Justice," associating everything with justice. These traits were directly transplanted to KAI. The first thing KAI did on his first run was to walk around Heavenhold and use its control to name the equipment so that they included the word Justice. For a while, this gave Heavenhold's workers a tough time because the equipment wouldn't operate unless they shouted Justice. KAI has since caused many other problems including preaching about justice and passion upon every encounter until the listener's ears ached. Nonetheless, because he was already one with the control system and many considered him to be kind of charming, it was decided he would stay that way.
Like the young Kaden, KAI also desired to be a Hero. On the other hand, KAI was also well aware that he could not become one because he was created for controlling Heavenhold and helping the Hero in danger. KAI tried to push the desire to be a Hero out of his mind so that it wouldn't interfere with his mission. But in the end, he couldn't give it up completely, so he secretly devised the Hero's pose that represented his ideal image of a Hero. Although the pose was somewhat embarrassing to some, KAI says striking the pose makes him feel like a Hero. He later described the pose as "a righteous and sacred posture that inspires courage and passion," and it is said that he always strikes the Hero's pose before operating an important equipment.
Following the completion of KAI's learning, KAI had to be put into hibernation at the lowest level of Heavenhold according to the original plan, for his purpose to be maintained and to prevent him from being modified. This was done in the presence of everyone at Heavenhold. It's said that even those who had criticized KAI for being noisy felt a kind of sadness at that moment. Right up to the moment KAI was put into hibernation, he reassured everyone that he could handle it. Although everyone there agreed that they wished to see him again, they also promised one another to create a future where KAI would never wake up.