an evil mist has gone loose, and every single person on the planet, has turned evil. The infected don’t talk, instead, they bite other people to turn THEM infected. Since goku was a saiyan, he couldn’t be infected, but all his friends, and his wife chichi were infected. Goku needed to find android 21 for the cure, but was injured due to the attacks. All the senzu beans were gone, since Korin has been infected. He’s all by himself