Timeskip

13 years later*

It was the day of his bending test he would have to duel multiple opponents using one element, he passed water quickly, showing precise control and skill. His earth bending excelled and he showed his mighty strength and sturdiness. His fire bending was clean and passionate. They would train him in air later with the Air Nomads. 

But he passed all three tests, showing fighting skills and qualities of an Avatar. From the beginning his training was focused on becoming a perfect Avatar which entitles strength and Spirituality. 

Katara then spoke.

"It's time for him to start training with Tenzin." 

The other instructors agreed.

"Thank you." 

Kyosuke said with a bow to his instructors. He had finished his training with every element except Air, now Tenzin the son of Avatar Aang and Katara.

'Retraining my power is hard.'

Ever since he started training he grew more and more powerful each day but restricted himself in public because being Avatar is all about balance and tranquility and not strength. But he would continue to get stronger while retraining himself because it was like he was continuing his avatar training with weights on. He only showed a small percent of his true unrestricted power before anyone, but then would leave on a small adventure outside the Southern Water Tribe compound, and bend unrestrained.

"Then I will take my leave."

He left the encampment and went through the Icy lands. He used water bending to to create a ice surf board and got on it while moving it through the icy lands. After traveling for 20 minutes at high speeds, he got off and then practiced his bending. He used Earth bending to move a large piece of the ground from the rest, it was still earth even though it was covered by ice, he then created a tsunami but then put the water back, then he shot fire from his hands and mouth which looked like 3 pillars of fire, he then lightning bended. His three elements were incredibly powerful, he could use advanced forms of all three but for blood bending he needed a living opponent and for metal or lava bending he needed metal or earth. 

After letting out his full power he went back. He then saw a flying bison, he assumed it was Tenzin but waited as Katara was approaching and decided to let them reunite as a family. After the flying bison landed he saw a bald monk which was Tenzin, his wife and three children.

After watching them for awhile, Tenzin saw Kyosuke and approached him.

"Kyosuke? Look at you so big and Strong."

He said, remembering the time when he saw him when he was a child.

"Thank you Master."

He bowed his head to his Air Bending Master. Tenzin had a complicated look and told him that he couldn't train her as he had to leave for Republic city. Kyosuke was a bit down from the unexpected news but he took it well. Kyoshi didn't use her air bending much anyway, but he still wanted to master all four elements but in the meantime he would hone his other three to a higher extent.

During dinner Katara asked the other instructors and Tenzin if I could go with him to the city. 

The instructors then contemplated, they were the White Lotus and the Previous Avatar Aang, tasked them to keep the next Avatar safe. But they also knew that Kyosuke was a Bending prodigy and he showed not just strength of an Avatar but the mindset and responsibility. 

"That's not a bad Idea but he still hasn't mastered all four elements and sending him away wouldn't be the best option." 

"It's not away, if any trouble comes Tenzin is there and plus Tenzin can continue to teach him as they go." 

They threw out ideas and eventually decided to agree. 

Kyosuke then went that night to his parents to tell them the news, they hugged him and then he left after a word of advice from the White lotus and Katara. 

Kyosuke Introduced himself and met with Tenzin's family.

His wife Pema was a kind and funny woman and a non-bender who was currently pregnant with their fourth child. Jinora the eldest daughter and a calm and curious girl, then Ikki an super energetic girl that was hyper and the middle child and the youngest child Meelo who was also very super energetic boy that liked to play a lot. 

We got on the Flying Bison and left for Republic city, through the journey I played with the kids and answered their questions and Tenzin also taught me some basic things.