On King Kai's planet.
"Kaioken," Goku yelled out as a crimson aura covered his body.
Kaioken is a technique that King Kai created that allows the user to multiply their power level by two times by putting a lot of stress on their body.
King Kai believed that the stress that the body undergoes would be completely negated and the multiplier would go even further beyond if one completely mastered the Kioken technique.
"Now try moving around. Remember you have to be careful." King Kai said.
"Right." Goku nodded as he started to walk.
Then he tried to run but after only a few steps he felt his whole body was in pain and his muscles started to ache.
"Ahhhh," Goku screamed out as his crisom aura disappeared and he collapsed to the ground.
"That is why I warned you." King Kai said as he walked towards Goku to help him out.
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A few days have passed.
Goku continued to train under King Kai and he has now perfected Kaioken's two-time multiplyer.
"Haa." Goku tried to use his martial arts in the air as he threw a rapid amount of kicks in his Kaioken form.
"You have improved a lot. I didn't even think that it was possible to completely master this technique." King Kai complemented Goku.
"Hehe." Goku smiled as he landed back on land.
"It is still very hard. I don't think I can start using this in combat." Goku said.
"So you are still not used to it." King Kai said.
"Then rest for a while we can continue to train after your body is fully rested." King Kai said.
"Kai Ohh sama, you said Dai also trained under you. Did he also learn Kaioken?" Goku asked.
"No, he refused." King Kai replied.
"I see," Goku said while looking a little disappointed.
"Well, I don't think learning Kaioken would help him much. After all the power he possesses doesn't seem like it is compatible with the Kaioken." King Kai said as he recalled Dai's Ikari transformation.
Ikari or Golden eye form is the transformation that Dai undergoes that increases his power level by ten times.
However, it also possesses its drawbacks.
First, the user's body was filled with a large amount of ki.
More than he would normally be able to handle during the transformation.
This causes the body to endure the user's overwhelming strength, which causes the user to accumulate a lot of stress for the body.
So Kaioken which is also straining the body was not going to be compatible with the golden eye form no matter how much one trains.
It was the conclusion that both King Kai and Dai came to when Dai was training under him.
"Just keep this between you and me. Although his transformation is stronger for now I believe if you perfect Kaioken you will be able to become even stronger than him." King Kai said to Goku.
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A day before the Saiyans arrived. Back on earth.
"So this is the place where he trained," Dai asked Kami as he stood in front of the entrance to the hyperbolic time chamber.
"Do you want to do this? I think this training will be hard for you even with the power that you currently possess." Kami said to Dai.
Dai nodded. Currently, this is the only training available on earth that might be effective for him.
During these months he has been travelling around the world to train his body and mind but it was not very effective as he was already too strong.
For him, this training is the only thing that he has not tried out.
He stepped into the time chamber as the door that acts as the entrance closed and disappeared.
He looked at the endless white void.
He then smiled noticing that the gravity and the atmosphere of this place were something that he never felt before.
The more you step into the void the harsher the gravity and the atmosphere becomes.
He didn't even have that kind of feeling while he was training on King Kai's planet.