The Boo of Pure Evil (純粋の魔人ブウ Junsui no Majin Bū, lit. "The Pure Majin Boo") is the five hundred eighth chapter of the Dragon Ball manga.
As the evil Super Buu continues to violently scream and morph in size due to the earlier removal of Good Buu's pod in his stomach, Goku, Vegeta, Dende, and Mr. Satan watch in complete confusion, wondering what Boo will become. On the Sacred World of the Kai, Old Kai and Kibito Kai also watch in confusion, although Kibito Kai has more of a clue about what's happening, stating that Boo is morphing back into his "Original state". Eventually, Boo finishes his transformation, and is now much shorter in height, with less muscle. Vegeta laughs at his new form, mocking him due to his kid-like size. Kid Buu does not respond to this insult, and instead stares blankly into the sky. Back on the Kai planet, Kibito Kai explains his first encounter with Boo while he was Supreme Kai and explains everything:
Millions of years ago, the evil wizard Bibbidi created Boo, who he sent to attack millions of planets across the galaxy, despite Boo barely listening to his creator. Supreme Kai, one of the five Kais who ruled over the universe, himself being the Eastern Kai, was the youngest, and the weakest of the Kais, who managed to escape Boo's wrath with injuries. Kibito Kai explains that the Northern and Western Kais were easily destroyed by Boo very quickly, lasting only a short amount of time. The next to die was the burly South Supreme Kai. Kibito Kai explains that Boo transformed into his buff form after absorbing the Southern Kai, the form seen when Boo earlier transformed. Old Kai asks for Kibito Kai to continue, after Kibito Kai turns in sudden sadness. Kibito Kai continues to explain that the next Kai to be absorbed was the Great Lord of Lords, Daikaioh, who loved to eat and had a playful, pure-hearted personality. After Buu absorbed the Grand Supreme Kai, he morphs into the Fat Boo, whose personality becomes much more playful due to his absorbee's personality. Calculating from his info, Old Kai realizes that the original form of Boo, who has now finally reappeared, is the most dangerous form, due to having no compassion or playful traits that Fat Boo had due to the Grand Supreme Kai.
On Earth, still staring into the sky, Boo suddenly without warning unleashes a deafening scream, much to Goku and Vegeta's surprise. Suddenly, Boo turns his attention to the ground, lowering his hand. He suddenly unleashes a small ki blast, shocking Goku and Vegeta, but Vegeta manages to deflect the blast just before the blast hits the planet. Enraged by Boo's action, Vegeta demands that Boo fight them first before even thinking of wiping out the planet. Boo turns towards them, finally changing his expression into a menacing smile. Boo then raises his hand in the air, and charges a gigantic energy ball, and despite Goku's pleas, Boo launches the attack giggling, preparing to destroy the planet. Goku and Vegeta suddenly become fearful, knowing there is no way they can deflect an attack that large and more powerful than themselves. As Goku notices he only has seconds to escape alive and be able to save Gohan, Piccolo, Goten and Trunks, Goku prepares to teleport to them, and then to the Planet of the Kais, along with Vegeta. As Goku puts his plan into action, he notices Mr. Satan and Dende down below. Not wanting them to die too, he grabs a hold of them, but now realizes he has no time to rescue the others. As Goku prepares to teleport to the Kai planet, Kibito Kai teleports to Earth himself and grabs Goku's hand, teleporting Goku and the others back to the Kai planet, as Gohan, Trunks, Goten and Piccolo are destroyed in the Earth's explosion. As Old Kai cheers their escape, Vegeta scolds Goku for saving Mr. Satan and Bee rather than his own family and friends, as Goku stays silent with a look of sorrow.
- The only Supreme Kais shown in this chapter are Supreme Kai, South Supreme Kai and the Grand Supreme Kai. The West and North Supreme Kais are mentioned, but not shown. They are, however, shown in the anime version of this scene.