Goku and Bulma stopped by a nearby shore to camp. Here they encounter a strange old man with a turtle shell. He's wearing a Dragon Ball as a necklace. His name is Roshi.
Immediately, Roshi sensed the ominous Ki that resides in Goku's Body. He estimates that this Ki is even greater than his. He treads carefully on his words and easily complies to give Bulma the Dragon Ball. Before Goku and Bulma leave, Roshi challenged Goku on a sparring match. Maybe he will get an insight of Goku's Character here.
Goku and Roshi go into a battle stance, without holding back, Roshi unleashes a Ki-Palm attack that pushes Goku back a few inches. Goku smiles and said,
"Ki. You must be strong. Have a taste of my Ki."
Goku smiled and performed a Ki Palm strike that is so powerful that it made Roshi cough up blood and spit upon contact. Roshi, now knows that this Kid is ruthless. He isn't pure of heart. Roshi goes into his buff form and tries to perform the Kamehameha.
Bulma is shocked to see the buff form and mutters,
"First a flying kid. Then, a talking cat. And finally this? A buffed up old turtle!"
Goku smiles and observes the technique. Absorbing the information and learning how to do it.
"Ka... Me... Ha... Me..."
Goku smiles and puts his arms open as if he's welcome to receive the attack. Sweat drips upon Roshi's head as he sees that this kid is reckless.
"Haaa!"
With a blinding light, a beam of Ki launches so destructive that it left damaged marks upon the beach sands. Goku was hit directly on his face. Smoke explodes upon contact. Roshi returns to his frail form, exhausted after the attack. As the smoke fades. It reveals Goku with very little to no damage at all. With that, he blitzes Roshi and says,
"Ka..."
Roshi, surprised to realize that this kid is trying to replicate his technique. But Roshi, with his Martial Arts expertise, he ducks down and kicks Goku's palms straight up, disrupting his charge and then performs a spinning round house kick that hit Goku on his temple. This shook Goku's brain causing him to have double visions with dizziness. Roshi lands a couple of pressure point attacks that immobilized Goku on the spot. The difference in technique and skill is massive.
"Phew. What a strong kid." Roshi sighs.
Roshi leaves the shore with a turtle and says to Goku,
"If you want to learn more about Martial Arts, come find me."
Deep inside Roshi, he was nervous. The thought of a young boy being so strong is what keeps him up at night. And to think this same boy easily replicates his techniques is scary to him.
The following encounter is within the Aru Village, where it was rumored to being ruled by a Monster. Goku, excited to try fight yet another strong guy, jumped head first into the fray. The Monster, thinking Goku is just a kid, tries to scare him, but Goku is fearless. With a single kick, the Monster was sent flying backwards and with a poof, transformed back into a small pig.
The villagers surround the small pig and demanded to return the girls and the money he stole. Scared of what Goku would do, he complies.
What follows is Goku and Bulma arriving at the Carrot Gang infested village. They came with a stowaway named Oolong. The transforming Pig. They were also being stalked by non other than Yamucha, who is curious as to why the kid is so strong.
Upon arriving, Goku immediately senses the sinister Ki that is in the village. Someone here is doing nefarious things. He uses his Qigong technique to scout the area. He spots a big Rabbit turning people into carrots. This infuriates Goku causing him to attack out of nowhere. He knocks out the Rabbit and demands to undo what he did. The Rabbit almost touches him, when Goku easily weaves out the way and knocks him unconcious. This returned the carrots back to being normal villagers. Goku ties up the Rabbit and his gang and casually throws them to the moon.
Yamucha on the background is in disbelief. Now he wants to know how to get that strong. But the young sexy girl is on the way... If only she wasn't there.
Thus, Bulma, Goku, Oolong and technifally Yamucha and Puar all set out to find the rest of the Dragon Balls.