This movie picks up right where The Legend of Shen Long left off (with the first movie being a retelling of the Pilaf saga, and this movie being a retelling of the first couple episodes of the Tenka-ichi Budokai saga)... Son Goku has left his new friends (Bulma, Oolong, Puar, and Yamcha, respectively) to go train with the Kame Sen'nin, Muten Roshi. Roshi isn't terribly enthusiastic about the prospect of taking in a pupil, when a second potential student arrives; Kuririn.
This part of the movie is exactly like the end of episode 14
(but with more detailed pornography)
In the end, Roshi consents to take on the student who can bring him a pichi pichi gal - but not just any pichi pichi gal, he wants the fabled Sleeping Princess of Devil's Castle (Title drop)! Located rrrrrrrrrrrrrrrrrreally far in the east, Devil's Castle sits on five tall mountains known as Devil's Hand. And to make things fair, Roshi forbids Goku from using Kinto Un. Though when Kuririn trips Goku as they begin their trek, it is clear he isn't fond of playing it fair.
They swim across oceans...
Race across fields...
Venture onto suspect bridges...
...and run with wild buffalo!
Meanwhile, Roshi enjoys porn.
(I told you it was detailed.)
Bulma, Oolong, Puar, and Yamcha arrive, looking to visit with Goku. They ask where he's gone (Bulma accuses Roshi of sending him on a perverted errand - granted, he did ask her for pafu pafu as soon as she arrived!), and Roshi tells them he and another boy have gone to... an Amusement Park! (the Devilishly Fun Castle - which is rrrrrrrrrrrrrrrrrrrrrrrrrreally far to the east!) So, not having anything else to do in this movie's plot, the B-cast heads off to Devil's Hand!
Back at the plot, Goku and Kuririn have arrived at Devil's Hand!
Yup. That's it.
So Goku and Kuririn enter the big, scary mountain range and find the Castle - which is full of spooky statues with eyes that watch you! Kuririn is skeptical of the whole thing, but Goku (being Goku) is too curious to stay in one spot for long. Shaggy and Scooby wander off to find a kitchen.
At this point, the B-cast (in Yamcha's flier) are attacked over Devil's Hand by a rather derp-looking Oni.
(Why does he have a vest of bullets and an extremely primitive hammer? Demons have developed firearms, but not a forge?)
Later, Bulma awakens in a strange and beautiful room, and is greeted by the handsome host of Devil's Castle, Lucifer.
And she's down for it.
Lucifer apologies for any discomfort she may have had upon arrival, and offers her to join them for dinner.
Elsewhere in the Castle, Kuririn and Goku get attacked by a massive army of Oni, and their General. Goku handles their general in a one-on-one brawl, while Kuririn battles the mindless hoards. But being the sneaky monk he is, Kuririn attempts to duck out of the fight while Goku is still neck-deep in Oni. This doesn't work out so well when Kuririn falls off a cliff, and is nearly devoured by a giant lake monster!!!
Thankfully, Goku is there to snatch him from the jaws of death!
Then Goku puts Kuririn on Kinto Un aaaaaand
Well, the important thing is, Goku managed to save him a second time.
When Goku scolds Kuririn about thinking bad thoughts (and as a result, not being able to ride Kinto Un), Kuririn says the most truthful line of the series: "I can't help it!"
The Oni General and his men, using spells to fly, come straight for Goku and Kuririn. But they aren't as lucky, and are swallowed whole by the lake monster. Ah, I love a clean ending.
Oh, right, he's gunna eat Bulma.
Oolong and Puar use their transformation powers to sneak into Lucifer's ceremonial hall (as Oni servants - with Puar having the additional charge of acting as a costume for Yamcha - proving again he's more useful than his "master"), and with Yamcha, they listen in as Bulma is about to be sacrificed to... the Sleeping Princess?! At this point, Goku and Kuririn come crashing into the room, blown out of the sky by a Rocket Launcher wielding woman...
It's Lunch! And she's stolen the Sleeping Princess (which is actually just a really big crystal)! Lucifer sends his hoards after her, and while the legion is distracted, Oolong, Puar, and Yamcha make to rescue Bulma. Goku and Kuririn run after Lunch (though the Sleeping Princess isn't a pichi pichi gal, they were still instructed to get it), and the hoards follow them when... Lunch sneezes.
For being in such a dire situation, she sure is cute as a button.
Goku grabs the Sleeping Princess, but Lucifer grabs Kuririn! Lucifer offers to trade, and Goku gladly accepts... but of course, when you make a deal with the devil, it usually doesn't work in your favor. The legion of demons stack onto Goku, and one manages to snag his tail... sending him down for the proverbial count.
Did I mention Yamcha, Oolong, and Puar were unsuccessful in freeing Bulma? Yeah, Yamcha's fault.
So the entire Dragon Ball crew is encased in a thick stone (except for Bulma, who is still to be sacrificed), as the Oni and Lucifer bask in their full moon ritual, which powers the Sleeping Princess.
Waaaaait... full moon?
Uh oh. Oh no.
Oh no no no.
No no no no no no no.
N- awwwwwwww fuck.
Oozaru Goku is on a rampage, and he cares not for friend nor foe. King Kong-like, he snatches up Lunch and basks in her as he pounds his chest. Then he decides he wants to eat her (and not in the way girls like). Kuririn brings up that Goku's weakness is his tail, and so Yamcha and Kuririn grab onto Goku's giant tail, hoping to bring him down. This only pisses him off, and causes him to seriously wreck some shit. Then Puar saves the day, by turning into scissors and cutting off Goku's tail.
I bet Puar wouldn't have gotten killed by a Saibaiman.
Back in the main castle, we find out what the Sleeping Princess is really for; to power a giant laser cannon that Lucifer intends to use to blow up the sun. Bulma points out that this would cause the oceans to freeze (expertly deduced, Bul Nye). Goku (tailless and wearing Oolong's pants) and Kuririn arrive to fight Lucifer (who can use ki blasts!) while Yamcha fights Lucifer's... butler (who has an axe that looks... kinda heavy, I guess...). Bulma shouts for Goku to destroy the machine, as it takes aim at the sun, and Goku does just that...!!
A well aimed Kamehameha takes care of that, and blows up Lucifer in the process!!
In the end, everything works out rrrrrrrrrrrrrreally well!!
Finally, the boys bring Lunch by the Muten Roshi, who approves and takes them on as pupils!
"I have a serious erection."