The reason Fang Zheng did this was certainly not out of kindness. On the contrary, he was digging a massive pit for Japan.
Obviously, if "Universal Flying Magic" could truly be completed, it would definitely spread into every aspect of life. And as long as Fang Zheng designed a backdoor into it, he would effectively hold Japan's lifeline in his hands. The same applied to the gravity-controlled fusion reactor. If Fang Zheng really invented that thing and Japan adopted it, he would be able to control the entire country's energy supply anytime, anywhere... Nothing could be more convenient.
So on the surface, everything Fang Zheng did seemed like he was stealing the protagonist's spotlight and completing the World Will's mission in his place. In truth, however, it was laced with deadly poison. Like a Trojan horse, if this world swallowed it whole, the power of life and death over the entire world would fall completely into Fang Zheng's hands.
As for how to create this "Universal Flying Magic," it was hardly difficult for Fang Zheng. This world did have flying magic. For example, many users of Ancient Magic could fly through the sky like Magical Girls. The problem was that it was their own unique personal power. It lacked universality and could not be taught to others, so it did not meet the requirements of "universal."
Fang Zheng had also studied this world's so-called magic and discovered that, despite its name, it was fundamentally much the same as Academy City's esper abilities. According to this world's rules, magic was an operation that altered event information itself—in plain terms, just like Academy City's espers, it used "Personal Reality" to overwrite "objective reality."
The so-called CADs, or magic devices, were essentially external automatic calculation devices. Magi would program something called a "Magic