Goku, Kuririn, Lunch, and Roshi move from one island to another (Kame House is conveniently a Hoi Poi Capsule) to begin training. They move an island with a residency of about 300, complete with a volcano and jungle. Roshi begins their training by testing their abilities. First, he tests their leg strength, by making them run a 100 meter dash. Kuririn runs it first, and scores a time of 10.4 seconds. Goku goes next, and gets a time of 11 seconds. Goku asks Roshi if he can try again, but with different shoes. Kuririn protests, saying Goku shouldn't blame his shoes, as Kuririn's monk attire isn't suited for running, either. That's when Goku shows that his toes are showing through his shoes... so Roshi gets him a new pair and permits him a second run. This time, Goku manages to score 8.5 seconds. Roshi is very impressed by his students, but tells them they have yet to surpass the Human Level... only when they are stronger than the strongest human, will they be great martial artists...!!
Roshi demonstrates by running the 100 meters in 5.6 seconds.
But when Kuririn goes to get Roshi a beer, Blonde Lunch chases him across the 100 meters... and he scores an 8.8 seconds! Not bad!
For their second test, Roshi inscribes a random stone with the Kame symbol (亀) and throws it deep into the heart of the jungle. He gives the boys 30 minutes to find the stone, with the loser missing out on supper. And if neither can find it in the allotted time, both miss out on supper. Goku is focused, diving head first into the jungle, and using his keen sense of smell to track Kame Sen'nin's scent to the stone. Kuririn is much more sneaky, opting to find a different stone, and draw his own Kame symbol on it, and take it back to the master.
But Roshi sees right through Kuririn's scheme.
Back in the jungle, the crafty Kuririn has one more plan ... When he sees Goku has found the stone, he talks our naive hero into letting him see the stone - to make sure it's the "real one"... when Goku's guard is down, Kuririn takes off with the stone, claiming victory. Unfortunately for the monk, Goku's stomach isn't to be trifled with.
They fight, and Goku wins easily. But instead of giving up the stone, Kuririn chucks it back into the jungle...!! Goku runs right after it, but Kuririn laughs to himself - having pocketed the real stone and thrown his fake! So Kuririn wins, and gets to eat supper with Lunch and Roshi.
And Goku watches in abject horror.
Fortunately for Goku, Lunch was tricked into buying a poisonous fish... and the following 24 hours everyone in Kame House, sans-Goku, suffers from painful food poisoning.
Goku probably finds a centipede to eat.