"The Mystery of the Kaio-ken" (界王拳の謎 Kaiōken no Nazo, lit. "The Mystery of the Kaiō-Ken") is the thirty second chapter of Dragon Ball Z and the two-hundred twenty-sixth overall chapter of the Dragon Ball manga.
Nappa is pissed, and Goku tells him “You ain’t in my league.” Kuririn and Gohan watch from a safe Nappa says Kakarrot made his head bleed, and asks him if he’s ready. Goku says this is the fight he wanted, and Nappa says he’s bluffing. Though Vegeta thinks otherwise. Nappa starts powering up and lifts his hand, causing the ground below Goku to explode. Goku manages to fly out of it, but Nappa spots him and flies after. Nappa punches at Goku, but Goku blocks it and kicks him in the face. The two exchange a few blows, and then they break.
Goku tells Nappa he’s gotten a lot better, and this just makes Nappa laugh and threaten to end this. Nappa fires a huge blast from his mouth at Goku, and just before it hits, Goku blasts it away with a Kamehameha. There’s a big explosion when the two blasts connect, and Vegeta is shocked that he blocked it in such a brief instant. Nappa can’t believe this, as that was his best technique. Goku says he’s a pretty tough bastard.
Vegeta yells at Nappa that he’s done enough, now he’ll take of it himself. Kuririn and Gohan are surprised that Vegeta will finally show himself, and wonder what kind of power he has if even the huge guy is scared of him. Nappa is pissed at this, but tells Goku that he’ll soon be sorry it came to this, for Vegeta is a genius fighter who was named after the Planet Vegeta. Nappa begins his descent, but then looks down toward Kuririn and Gohan and dives toward them. Goku realizes what he’s doing and that he won’t be able to make it in time.
Goku yells “Kaiō-Ken!!!!!”, suddenly speeds up, hits Nappa in the back, and then stands on the ground, catching Nappa. Goku holds him over his head with one hand, and then throws him to the ground right in front of Vegeta. Goku says he can’t fight anymore, and tells Vegeta to take him and leave Earth. Vegeta thinks, “What was that just now… In just an instant his speed and power suddenly grew!!”