Lesson Number One (父さんすげえや! 究極の必殺技·界王拳, To-san Sugee ya! Kyukyoku no Hissatsuwaza・Kaio-ken) is the 23rd episode of the Vegeta Saga in the uncut Dragon Ball Z series. The episode first aired on December 6, 1989.
Though severely outclassed by Goku, Nappa stubbornly refuses to give up, and continues to attack Goku. Goku dodges Nappa's attacks with minimum effort, blows away a Nappa's ki blast with a kiai, and manages to land several blows on his opponent, one for each of his fallen friends. Nappa almost loses control over his rage, but Vegeta angrily orders him to calm down or else he will have no chance of winning if blinded by rage. Nappa powers up to his maximum and fires a blast at Goku, who dodges into the air. Nappa gives chase and briefly engages Goku in battle, impressing the young Saiyan, but still unable to best him. As a last resort, Nappa fires a Break Cannon, but Goku easily counters it with a Kamehameha wave and cancels it out, leaving Nappa in shock. Just as Goku prepares to use the Kaio-ken to finish Nappa before things get out of hand, Vegeta furiously orders Nappa to forfeit.
Consumed by rage, Nappa goes for Krillin and Gohan out of spite. Goku gives chase but quickly realizes he will not reach Nappa in time. As a final resort, Goku uses the Kaio-ken Finish and incapacitates Nappa by breaking his back and throwing his limp body at Vegeta's feet. Though Krillin congratulates Goku for defeating Nappa, Goku tells him that the extreme strain from the Kaio-ken attack could have destroyed his body, which is why he took this long in using it to take Nappa out. Goku demands that Vegeta leave Earth and get Nappa medical help, but Vegeta refuses, and the final straw occurs when Nappa pathetically begs for help. Outraged, Vegeta takes Nappa's hand in his own, but throws him into the sky and fires a powerful blast which hits Nappa and obliterates him completely, angrily telling him that perhaps Nappa wouldn't have been such a disappointment with his death.
With Nappa finally defeated, Vegeta sets his sights on Goku, who orders Gohan and Krillin to return to Kame House. Before they leave however Krillin suggests that Goku should take the fight with Vegeta to another location as the battle could mess up their friends bodies if they came back to life. Goku questions how they could even be brought back now that Kami is dead and the Dragon Balls have disappeared forever. Krillin tells him that if he is able to beat Vegeta then he will clue him in on the details later. Krillin and says his farewells to Goku as he descends to tell Vegeta that they are going to fight elsewhere.
- Nappa is killed by Vegeta.
- Goku vs. Nappa
- Spirit Boost
- Double Axe Handle
- Volcano Explosion
- Break Cannon
- Galaxy Breaker
Differences from the manga
- Bulma and the others watching the battle at Kame House is exclusive to the anime.
- The anime shows a flashback scene to Goku's training on King Kai's Planet where King Kai described the risks of the Kaioken technique. In the manga it is only explained by Goku to Krillin and Gohan.
- This episode marks the first appearance of the Kaioken.
- In the Funimation dub, Nappa proclaims that he was the Commander-in-Chief of the entire Saiyan army. In the original version, Nappa doesn't say anything.
- Goku's four hits against Nappa could be compared to the attacks Kenshiro landed on his adopted brother Jagi in Fist of the North Star. Goku lands hits for Yamcha, Piccolo, Chiaotzu and Tien Shinhan while Kenshiro lands ones for his deceased rival Shin, his fiancé Yuria, two brothers he recently encountered and his own rage.
- In the Funimation dub, Krillin warns Goku that grabbing Vegeta's tail won't work. In the original version, like the manga, he instead suggests Goku take the fight with Vegeta elsewhere so that their friends bodies won't be mangled up if they are able to bring them back to life.