Mr. Money (fulfilling his duty to nomenclature by being obscenely rich) is holding a Budokai! In honor of his son Dolls 10th birthday, fighters are invited to come from around the globe to participate in a tournament where they will face terrifying aliens.
(By aliens, I mean illegal aliens.)
And the winner of the contest will get a one hundred million zeni, a family-sized tour of the worlds hotsprings, and a chance to challenge the strongest man on Earth... The hero of the Cell Games... Mr. Satan!!!
SA-TA-NU!! SA-TA-NU!!
Competing in the tournament is none other than the Z-senshi!
Kuririn.
Trunks.
Son Gohan.
Tenshinhan.
Piccolo.
And Yamcha.
... well okay, Yamcha was competing.
And in Other World, Kaio-sama and Son Goku watch excitedly.
(And Goku is jealous he doesnt get to enter because hes dead.)
Meanwhile, Muten Roshi enters his own competition: Hittin on ladies.
Mr. Satan recognizes our heroes in the preliminaries.
... and it puts him a little on edge.
Gohan, Trunks, Tenshinhan, Piccolo, and Kuririn all make it to the semi finals, along with fighters Dosukoi, Kung Foon, and Udo!
Udo is disappointed to have Gohan for an opponent.
He just doesnt know why, yet.
Spoiler: We never see Udo again.
Tenshinhan vs Trunks.
Surprised to see these two fighters flying around with colorful auras, the media goes to Mr. Satan for comment. Its just a trick, he says!
Vegeta turns off the TV, where he had been watching the tournament, at this point. According to Bulma, he hasnt been the same since Goku died.
Trunks wins!
Suddenly, Mr. Satans stomach begins to hurt!
... though truthfully, he was just looking for an opportunity to escape! Understandably, he doesnt want to fight the Z-senshi.
But as he rounds the stairs, he runs into a mob of fans.
And Mr. Satan cant resist his fans.
Piccolo vs Kuririn.
Irritated that there arent more challenging opponents, Piccolo throws the match (and Kuririn).
Going through the plumbing, Mr. Satan finally finds the exit of Battle Island!
... but it is, after all, an island.
Looks like youre stuck defending your title, Mark.
Then the final round starts! The finalists, Dosukoi, Kuririn, Gohan, and Trunks ride shuttles to various Battle Zones where challengers from ~another world~ are waiting for them. (Theyre actually just Mr. Satans pupils.) First one to beat their opponent and come back, wins! Kuririn thanks his lucky stars! He wont have to fight Gohan in order to win, so hell actually have a chance!
And sure enough, Kuririn is the first to meet his opponent.
A cute girl! But just because shes cute, he cant go easy on her!
(No need to worry about that, mate.)
These are supposed to be Mr. Satans pupils...
... but something most wicked is afoot...
Despite it being a game, these alien challengers are out for blood!
Frightened for their safety, the people of Battle Island call on Mr. Satan to come and save them! Hes a bit preoccupied, pretending to have to poop. (I used to do this to get out of going to school.)
Strong as his challenger might be, Trunks is stronger!
But someone even more fearsome lurks in the shadows!!!
Unable to resist his fans cries, Mr. Satan prepares to enter the fray!
Kaio is certain that the earth is now in grave peril, and its Gokus fault! Long ago, Bojack and his crew Bujin, Bido, Zangya, and Gokua (no really the guy Trunks killed is name Gokua) traveled through the four galaxies, conquering them at their whim. So the four Kaios banded together and imprisoned them. And by breaking Kaios world during his fight with Cell, Goku has unwittingly unleashed Bojack and his cronies onto the universe.
But the earth still has Gohan, so Goku isnt worried.
His friends defeated, Gohan is introduced to Bojack... personally.
Yamcha and Tenshinhan arrive to lend their aid.
"You think that were just going to let you have it your way?"
Bojacks crew explains that theyre here to take over the earth by force, as the most beautiful planet in the North Galaxy.
"Bojack-sama is invincible throughout the galaxy!"
"Dont underestimate us!" Yamcha retorts.
(Well... good try, boys.)
Its up to Gohan to fight off these monsters!
Try as he might, however, Gohan is no match for Bojacks crew.
(Cue the entrance music.)
Now that someone interesting as shown up, Piccolo reenters the fight!
Trunks steps in to defend Piccolo, but is caught in Bujins telekinesis.
... that is, until Vegeta arrives!
Despite losing his will to fight after Gokus death, Vegeta comes to assist in this crisis. ("Just... not bein a dick.")
Trunks catches his father from Bojacks assault.
("Nope, actually bein a dick.")
Bulma and Chichi watch the fight with the spectators.
With no one else to defend him, Gohan is caught in Bojacks crews telekinesis.
... but worry not!!!
Mr. Satan has arrived...!!
But from his arrival, the telekinesis is broken. Way to take one for the team, Mr. Satan.
However, Gohan just cant compete with Bojacks superior strength!!
Tired of watching his son get clobbered, Goku teleports from the Next World!
He lays Bojack out...
... and then he tells Gohan to stop acting like a child and use his full strength.
... and so, Gohan does.
Gohan easily defeats Bido and Bujin.
Confusing shippers and fanfiction authors everywhere, Bojack kills Zangya.
And then he takes aim at Son Gohan.
But the Super Saiyan 2 Gohan is too much for the space pirate to handle.
Unleashing a final Kamehameha...
... Gohan rams straight through Bojack, defeating him once and for all.
And that, kids, is how Mr. Satan saved the earth again.