In the game, the final goal was to deal with Junko Enoshima, but Fang Zheng clearly had no intention of following the game's script here. In their current situation, a mystery game was definitely impossible to play through properly, but that didn't mean he had no other options.
Fang Zheng knew that, in the game, there was an incident where Kyoko Kirigiri discovered a secret door in the innermost stall of the men's restroom. (Don't ask why Kyoko Kirigiri, a girl, was in the men's restroom.) She then told Makoto Naegi about it.
Makoto Naegi went to investigate the secret door and discovered hidden student records inside. Just as he was about to look through them, someone wearing a mask knocked him unconscious from behind.
That person was actually Junko Enoshima. She had originally intended to kill Makoto Naegi and frame Kyoko Kirigiri for it. It was a pretty good plan too, because Junko Enoshima had already died in the game. If Makoto Naegi had been murdered, everyone really might have treated Kyoko Kirigiri as the culprit. As Fang Zheng had said, no one would suspect a dead person.
Then, according to the rules of the "class trial," they would all be cremated for choosing the wrong culprit. Junko Enoshima, the real killer, could easily claim victory.
Unfortunately, Makoto Naegi's title of "Super High School Level Lucky Student" wasn't just for show. Before Junko Enoshima could make her move, Kyoko Kirigiri arrived. Junko Enoshima had no choice but to flee.
Now, Fang Zheng planned to have Makoto Naegi try to trigger that event. Of course, he wasn't sure whether it would work. If it did, that would be ideal. The instant Junko Enoshima appeared, Fang Zheng could send her back to her hometown to get married, and everyone could happily