Without the invitation from the Hero League, Heero was planning to train more people in his academy.
After the battle against the specters, he realized that the Hero League was far weaker than he thought to be. He was overestimating their capability all this time.
Even a group of low-ranked specters smashed the Hero League with ease. Most of the Gold Class Hero was nonsense. They were just too weak, struggling hard while facing the Level 5 Specter.
He could not imagine what if a bunch of high-ranked specters attacked the city. He was certain it would be a one-sided slaughter.
Now the Hero League offered to be Supreme Sun along with the great benefits. It was said that the Supreme Sun was a special position. No regulations or law shackled the Supreme Sun. It was not exaggerated to say that you could do everything you wanted to.
Of course, there was another reason why he wanted to accept the Supreme Sun position.