Over the following days, Son Goku had Trunks remain in his Super Saiyan form for as long as he could each day.
At first, Trunks could maintain his Super Saiyan form for half a day without fighting.
After two weeks, he could barely manage twelve hours. After a month, he could maintain it for an entire day.
Seeing this, Son Goku began sparring with Trunks.
They sparred for two hours every day, and the time Trunks could maintain his Super Saiyan form immediately dropped.
After three months of this, Trunks could fight Son Goku in his base form for half a day while remaining a Super Saiyan, and still maintain the transformation afterward.
A year later, Trunks finally perfected Super Saiyan 1, reaching full power.
By then, Trunks's power level in his Super Saiyan Full Power state had surpassed Son Goku's base power level, reaching 1.5 billion.
Because Son Goku had spent that year training Trunks rather than focusing entirely on his own training, his power level had not grown much. It had increased by only 100 million, bringing his base power level to one billion.
Once Trunks had reached Super Saiyan Full Power, Son Goku began teaching him how to transform into Super Saiyan 2.
"There are two ways to transform into Super Saiyan 2," Son Goku told Trunks. "One is to push your power level to its limit, at which point the transformation will come naturally. The other requires extreme rage. In your current state, you can only use the second method."
"Uncle Goku, are you saying I can transform into Super Saiyan 2 through extreme rage?" Trunks asked.
"That's right," Son Goku said. "I think you already have some experience with that. Think about something that makes you furious."
Trunks nodded and began recalling the things that made him angry.
He remembered how Son Gohan, his mentor and older-brother figure, had fought the androids alone to cover his escape and been brutally murdered. He had been powerless to help, fleeing in desperation like a coward. Rage welled up inside him and surged toward the heavens.
Trunks seethed with anger and hatred. He hated the androids' cruelty and cold-bloodedness, and he was furious with himself for being a useless weakling who could not stop their atrocities.
When his rage reached its peak, Trunks let out a roar. "Aah! Aah! Aah!" Golden flames of energy erupted around him. His hair stood upright, with one golden lock hanging over his forehead, and lightning coiled around his body. His green eyes and stern face bore a bloodthirsty, cold, merciless expression.
Seeing this, Son Goku smiled. "You did it, Trunks. You've transformed into Super Saiyan 2."
Feeling his newfound strength, Trunks said excitedly, "So this is the power of Super Saiyan 2! It really is twice as strong as Super Saiyan 1. Thank you for teaching me, Uncle Goku."
"You're welcome, Trunks," Son Goku said. "We still have ten months left. Use the same method you used to train Super Saiyan 1 to full power, and try to perfect Super Saiyan 2."
"Got it, Uncle Goku," Trunks said. "Aren't you going to train with me?"
"Trunks, I'm going to work on Super Saiyan 3 next, so you'll have to train on your own," Son Goku said.
Trunks was stunned. "Uncle Goku, are you saying there's another transformation beyond Super Saiyan 2?"
"That's right, Trunks," Son Goku said. "The path of training never ends. Never mistake your little corner of the world for everything there is."
"I understand, Uncle Goku," Trunks said.
Son Goku nodded, then flashed away to one side and began training.
With a shout, Son Goku transformed into Super Saiyan 1, immediately followed by Super Saiyan 2. Then he began roaring at the top of his lungs.
"Aah! Aah! Aaaah! Aaaaah! Aaaaaah!"
As he roared as though straining with constipation, Son Goku's energy skyrocketed. Hearing him, Trunks sensed his energy and found it as imposing as a mountain and as vast as the sea. Compared with it, his own Super Saiyan 2 energy was no more than an ant.
Trunks was deeply shaken by Son Goku's strength.
What Trunks did not know was that this was only the tip of the iceberg of Son Goku's true strength. Compared with Son Goku using a three-thousand-fold Kaioken, Super Saiyan 2 was barely worth mentioning.
After three full minutes of roaring, Son Goku's appearance began to change.
His golden hair grew longer until it hung down to his waist. His eyebrows vanished, his brow ridge protruded, and his eyes turned dark green, becoming even colder and more merciless. Golden light enveloped him, and the lightning surrounding his body grew denser than it had been in Super Saiyan 2.
Trunks stared, dumbfounded, as Son Goku turned to look at him.
That stare alone left Trunks drenched in cold sweat, his legs trembling.
Seeing his reaction, Son Goku smiled. "What's wrong, Trunks? Don't recognize me after just a few moments?"
Trunks let out a long breath. "Uncle Goku, do you realize how evil you look like this? You look more like a villain."
"Oh, really?" Son Goku said. "I think this form looks pretty handsome and cool. What do you think?"
Trunks looked him over again. "Now that you mention it, Uncle Goku, it really does look handsome and cool. Not only that, you look pretty imposing, too."
Son Goku nodded with a smile. "This is Super Saiyan 3. Trunks, there's a vast road ahead of you, and training never ends. Keep at it, young man."
Trunks nodded. "I understand, Uncle Goku. I'll train hard."
"Go on, then. Get back to training, Trunks," Son Goku said. "Try to reach Super Saiyan 2 at full power before we finish our secluded training."
Trunks nodded, flew away from Son Goku, and began training.
Once Trunks had started training, Son Goku began his own training as well.
He needed to master the Super Saiyan 3 transformation first before exploring anything else.
Three months later, Son Goku had mastered the Super Saiyan 3 transformation and began working on his special techniques.
Three months later, Son Goku stood in his Super Saiyan form with his eyes closed, his energy churning around him. Suddenly, he opened his eyes and spiraled upward, shouting, "Ten Thousand Swords Return to the Origin!"
Golden energy swords shot out from all over Son Goku's body in an unending stream, leaving no blind spots.
Watching from a distance, Trunks stared in amazement, his eyes shining. Uncle Goku's move is so cool! I have to get him to teach me!
Only after unleashing hundreds of thousands of golden energy swords did Son Goku stop and slowly descend to the ground.
Trunks immediately ran over. "Uncle Goku, that Ten Thousand Swords Return to the Origin move was so cool! Can you teach me?"
"I can," Son Goku said, "but this technique is very difficult. Do you still want to learn it?"
"Yes, of course I do!" Trunks said.
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