The journey between Goku and Master Roshi it’s been quite long. The Saiyan warrior meets one of his most important senseis in the first arc of dragonball. The martial arts expert doesn’t let anyone into the turtle school and we all knew that this little guy with a tail was anything but normal.
However, Roshi didn’t know that yet. And despite the fact that Goku wanted to receive strict training to increase his powers, the teacher was not going to let him in so easily, despite knowing that he was Gohan’s grandson.
For many, the simple fact that Goku was able to execute the Kame Hame Ha without much effort could be the main reason why Roshi decides to train him. But the reality is that there were a couple of previous situations that consolidated the relationship between these two characters, one of the most important in all of Dragon Ball.
What happened before that first Goku’s Kame Hame Ha?
That Kame Hame Ha was just a confirmation for the Master Roshi realized the power that Goku was capable of reaching. But the real reasons why he trains him occurred when the little warrior saves the tortoise.
The big man with a shell, guardian of Kame House, was going to be eaten by a giant tiger. Goku saves him and then Roshi does a crucial action for the stories: he gives him the Flying Cloud.
When the then little boy was able to climb up, Roshi noticed that he was pure of heart and the fact that he had previously saved Tortuga confirmed it. The Master already knew that he would have a new disciple without the warrior knowing it.