Disclaimer: I don't own Naruto or Boruto. Kishimoto does.
Chapter 1: A Master and His Apprentice
Clang! The sound of metal on metal rang through the forest. Boruto jumped back, shifting his katana into his left hand. He made a few one handed seals and his hands filled with electricity. The katana in his hand became charged with his lightning chakra, and Boruto bolted (no pun intended) at his master. Sasuke backed up into a tree, wanting to make Boruto think he had cornered him. He activated his Rinnegan and readied himself, closing his eyes.
Boruto expected this, but didn't let it show, continuing his dash. Sasuke opened his left eye, his Six-Tomoe Rinnegan flashing. Boruto knew exactly what Sasuke was going to do. He sprung into the air right as Sasuke's ability Amenotejikara kicked in, catching him mid-leap. The jutsu warped Boruto right in front of the tree. Boruto, still being lifted upwards from his jump, stepped onto the tree. A bit of his chakra flowed to his feet, and he ran up it.
[Fire Style: Great Fireball Technique!]
A giant ball of fire rushed at the tree, and Boruto realized he couldn't escape it. But…. Boruto jumped off the tree and backflipped, activating his Jougan. He promptly warped behind Sasuke, narrowly avoiding being incinerated. Sasuke wheeled around, his Eternal Mangekyou shining.
[Amaterasu!]
Boruto warped away, dodging the black flames. Sasuke kept at it, the ground becoming coated with black fire. "How will you evade this?" Sasuke asked.
Boruto grunted, throwing his katana high into the air. He raised his right hand and formed the ram seal. Nine shadow clones appeared around him, each with their Jougan activated. "Let's do this guys!" Boruto yelled, his clones nodding.
Each clone held out their hands, Rasengans forming in them. The moment the Rasengans formed, Boruto grinned. Three Boruto clones added their Lightning Chakra to their Rasengans, making the Lightning Release: Shockwave Rasengan. Three other clones added Wind Chakra to theirs, forming the Wind Release: Spiraling Tornado Sphere Rasengan.
The remaining three clones added Water Chakra to their Rasengans, creating the Water Release: Great Flood Rasengan. Then the real Boruto added Fire Chakra to his two Rasengans, creating the Fire Release: Blazing Sphere Rasengan. Boruto nodded to his clones, and they all warped around Sasuke. Unbeknownst to Sasuke, Boruto had created more clones with Fire Release Rasengans than he'd seen, and they had warped into the trees.
"Fire!" Boruto yelled. A barrage of Wind Release Rasengans bombarded Sasuke. He jumped into the air to dodge, but that was the trick to the Wind Release Rasengan. When it hit something, the Wind Chakra would come out as a whirling wind, hence the Spiraling Tornado part of its name.
Sasuke was caught in the resulting whirlwinds, spinning around violently. The wind died down and he fell to the ground. Very good, Boruto, he thought. Your skill has improved in the three years we've trained. But Sasuke had little time to reflect as a flurry of Lightning Release Rasengans flew at him. He got to his feet, spotting a stick a couple feet away from him. His Rinnegan charged, he used his special ability, Amenotejikara.
He switched places with the stick, narrowly dodging the balls of chakra. But, as with all Boruto's Elemental Rasengans, Lightning Release Rasengans had an effect. The moment they hit the ground, yellow and blue electric shockwaves coursed through the ground, shocking Sasuke. The Borutos jumped to avoid the electricity, preparing their next Rasengans.
What's next? Sasuke thought, looking around. Water Release Rasengans showered him, and he outstretched his arms. "Almighty Push!" he said, and the Rasengans flew away from him. They hit the ground, exploding into gallons upon gallons of water.
Then, right as the water was created, Fire Release Rasengans rained upon Sasuke from literally every direction. Sasuke, now foot deep in water, raised his hands. "Susano'o!" he yelled, and a purple rib cage formed around him. The Rasengans impacted the Susano'o, lighting it on fire. "What the-" Sasuke was cut off by a yell above him.
An enormous Rasengan was closing in. How did I miss that?! Sasuke asked himself. He quickly increased his Susano'o to Complete Body. Sasuke met the Rasengan head on, a huge explosion following. Sasuke's Susano'o disappeared after the explosion, and he used a wind release to clear the smoke. Boruto was on one knee, panting, his katana on the ground.
Sasuke walked up to him, helping him up. "Impressive. You've exceeded my expectations with your improvement. I never expected you to get this far, even as a fifteen year old. Then again, neither did I expect your idiot father Naruto to become the most powerful Genin-I mean Shinobi, in the world," Sasuke said with a light chuckle. Boruto smiled at that, picking up his katana and sheathing it.
"Can we return to Konoha?" Boruto asked. "I'd like to see Himawari and the rest of my family and friends again,"
Sasuke nodded, forming his Complete Body Susano'o once more. "Let's go," he said, hoisting Boruto into the confines of the Susano'o. Its wings formed, and they took off into the skies, homeward bound.
Endnote: Whew! How did you like that? The story's set three years after somewhere between the Momoshiki arc and the Mitsuki arc. For those of you that came for BoruSara or simply Sarada, yes, there is all of that. In the upcoming chapters we'll be seeing Himawari, Mitsuki, and your favorite character; Narut… Just kidding. It's Hinata.
Peace!
YellowFang