The new Yellow Dragon Emperor, murderer of Sun Gohan
Long Di was Sun Gohan’s other star student and Sun Wuying‘s rival. He was driven from the school because of his harsh moral views, bordering on cruelty (like Ender from Ender’s Game).
He returned to the martial arts school, and defeated many of Master Sun’s students. Master Sun stepped in to face him, and because Long Di wielded a magical sword, he was able to strike down Sun Gohan. Sun Wuying fled the school as Long Di’s soldiers approached, and he saw it burn from a distance.
(Long, as it turns out, means “Dragon” in Han)