Disclaimer: I don't own Naruto or Dragon Ball bla bla bla…

A/N: What would happen if some divine force swapped Naruto with Goku at the beginning of the story while replacing Naruto with Goku in the Narutoverse's memory and administration (so no one will find anything weird)? This is Goku post Taopaipai fight.

Goku doesn't remember anything but his name and abilities. He is thrust into the Mizuki fight out of nowhere at the moment Iruka shields him with his body.

Goku gets his magic staff.

X

Chapter 1

Goku was pushed to the ground, a tanned man with a bandana crouched over him. The man started spewing out absurdities that he didn't understand, talking about being just like him, a prankster without parents who used his pranks to draw attention.

"What are you talking about? I'm not a prankster."

The man looked surprised, but soon was called back to reality by another man who seemed to be trying to kill them. The tanned man deflected his attacks with a weird pointed tool.

"Hey! You! You tried to save me from the blue haired guy, right?" asked Son Goku without formalities.

"What?" asked the two men at the same time.

"You risked your life for me, I won't let you die."

"Hahaha!" laughed the blue haired man. "As if the dunce of the class could help against a chûnin! I'll kill you right after I finish Iruka!"

The guy nearly stabbed the black haired man, but Goku had appeared and kicked him away. The blue haired man's attack hit nothing and Goku's knee hit him in the guts, folding him in two and sending him flying ten meters backwards and tumbling a few times before being stopped by a rock. His head had cracked the stone and the blood running from behind his head indicated a hemorrhage.

"How…how did you…?" tried to ask the black haired guy.

"Weak," commented Goku. "I barely put any strength into that attack."

He looked at the man in green vest who was staring at him with bulging eyes.

"What? Is there something on my forehead?" he asked, squinting to try and see what the man was staring at.

"You…you defeated a chûnin in one hit and you're telling me you barely put any strength in that attack? Were you holding back for the entire academy?"

"Huh? What's academy?"

The man was stunned.

"What is my name, Goku?"

"I don't know...wait, didn't the dead guy call you Iruka? Is that your name?"

"Goku, I have been teaching you at the academy for the last three years, how can you not remember my name?"

"Wait, how do you know my name? I don't know you."

"…I think we will need the Yamanaka clan to solve this problem…" concluded the man. "Please follow me to the Hokage tower."

"Okay. Is there something to eat there?"

The man facepalmed.

X

After a meeting with the master of the local martial artists village, it was decided that Son Goku would have to follow an accelerated course over the next week to catch up with the most important aspects of shinobi life and would be put on the team with a missing member.

As long as he got to fight, Goku was fine with it. After all, all that mattered to him was to fight strong people and kick the asses of the bullies.

He didn't understand chakra at first, but then he understood that it was pretty similar to ki, so he just had to learn how to copy the techniques of the shinobi with ki. Iruka tried to teach him clones, substitution and transformation. Son Goku failed but was able to produce afterimages with his raw speed, which Iruka accepted to overlook.

In order to test his martial arts and physical capabilities, Iruka asked a man that made Goku laugh with his helmet haircut and his green clothes. The man was named Gai Maito. Goku saluted him respectfully before the fight started.

Goku wanted to test his opponent before deciding what level he should fight at. The two fighters started circling around each other.

"Come at me, Goku! We are evaluating your skills, not mine! Show me your youth!"

Goku lifted an eyebrow at the weird choice of words, but he decided to go in. He'd just have to adapt his strength to his opponent.

He jumped on the green man and kicked him in a jumping axe kick with the same strength he had used against the blue haired guy he had killed in one hit. The man blocked the blow and Goku used the energy to bounce off his opponent's forearms.

"What a youthful lad!" exclaimed Gai in reaction to his attack. "Is that your limit?"

"I was holding back. Last time I used this amount of strength, I killed the guy in one hit. He was a chûnin. What are you?"

"I'm a jônin, lad. I'm also not in the same playground as the ninja you've killed! Don't hesitate to use more strength with me!"

"You asked for it," declared Goku.

He took his serious stance and started running around Gai, leaving afterimages in his tracks.

"Oh-ho! You remind me of my apprentice! When he removes his weights and uses the ability I taught him, he moves like you!"

Goku jumped the jônin and started a rapid chain of blows that the man blocked and deflected. After a few instants of this, he performed a backflip and stopped.

"You're not half bad, Gai Maito," he complimented the shinobi.

"You're very strong, Son Goku!" replied the other man. "I'm excited by this spar! Was this your limit?"

"I'll remove my weights, then I'll show you half of my real power. You're a worthy opponent."

"Then I'll remove my own weights! I won't use any forbidden techniques against you, but I'll show you my maximum normal strength!"

The two fighters removed their weights, Goku getting freed from sixty kilograms, the weights cracking the ground, Gai getting freed from even more weight, causing bigger cracks on the ground.

Iruka's eyes were bulging on the sideline. He couldn't believe that this boy had just graduated the academy as the last of the class. He had virtually remembered none of the classes he was supposed to have been in, but his taijutsu and physical stats were enough to make him a special jônin already, and he had just proved that he had been weighed down by heavy weights. Just how strong was he?

Gai and Goku went at it again, leaving dust in their tracks. Iruka couldn't see anything.

Goku could follow Gai's movements, they were relative in speed. Gai seemed to be strong, but Goku let an attack get him to gauge its' power and it barely damaged him.

"Are you using chakra to enhance your body? Martial artists use their ki to enhance theirs all the time," he said.

"I am, and it seems that your ki is offering way more durability than chakra can ever hope to give! This is impressive! Would you teach me how to use ki?"

"I'm no master, but I can try. My training is mostly physical and using the kamehameha."

"What is the kamehameha?" asked Gai.

Goku placed his hands on his right side.

"Ka…me…ha…me…ha!"

His ki beam manifested towards the sky and destroyed a few treetops on the way.

"This is the kamehameha."

"What a youthful technique! Since it is not based on chakra, my youthful apprentice might even be able to learn it if you agree to pass it down to him!"

"Sure, if he's like you, I don't mind."

"How much strength did you use in our last exchange?" asked Gai.

"Not everything, but I was quite serious."

"Do you have an idea of the percentage you used?"

"Percentage? Is it food?"

Iruka facepalmed and Gai lifted an eyebrow before bursting in laughter.

"Percentage means the part of something. You cut something in a hundred equal parts and each part is one percent. Sixty parts are sixty percents. Fifty parts are fifty percent, which is half of a hundred percents. Seventy-five parts are seventy-five percents, three fourths of a hundred percents."

"Is it like cake slices?"

"Exactly!"

"Okay, I understand. Then I think I was around two slices if I cut the cake in three."

"Sixty seven percent, two thirds? Interesting! And you could take one of my attacks head on without suffering any damage! What a youthful lad! I really hope you can pass down your teachings onto my apprentice and myself!"

"Yep! I'm already excited at the idea of a rematch if you become stronger!"

"If I used my forbidden technique, I could be a hundred times stronger than this, but it hurts my body, so I don't use it for friendly spars."

"I see. I hope I can fight against you at your full power one day, at least the maximum you can use while not hurting yourself too much!"

"Maybe your ki will offer me a new perspective and it might allow me to improve this technique! Who knows? It is only speculation, but I'm excited at the idea of a new source of strength and of more training!"

"Me too!"

Goku saluted and Gai did the same.

"Alright, Goku, let's put the kamehameha in ninjutsu… a 4/5, powerful and long range, but not very versatile and can't be used on weaker opponents without killing them. Taijutsu 5/5, genjutsu 1/5 for your afterimages. Total score, 10/15. Congratulations! You pass! You will be put on team seven at the beginning of the next week. I will show you where to go for the meeting and then where you live."

"Okay."

X

The next Monday, Goku entered the classroom, his head protector attached to the strap of his staff scabbard. The girls were loud so he went to sit beside a silent boy with black hair. A pink-haired girl tried to move him to sit in his place, but he didn't budge an inch. She gave up after a few seconds.

Iruka shouted to get everyone to sit and be silent before announcing the teams. Son Goku already knew what team he would be placed on, but he discovered his teammates at the same time as everyone else. He eyed the girl with a lifted eyebrow, then the boy and shrugged.

They waited for hours for the jônin who was supposed to be their captain to show up. After sleeping for a while, Goku moved the desks and chairs to exercise for the next hour. The jônin finally showed up to see him do one finger push-ups with his left pinky.

After a lame and disrespectful introduction, he told them to join him on the roof. Goku was there before everyone and looked at the man in disappointment when he arrived several seconds after him.

"You're slow," he commented.

"Then it just means that you're faster than me when I'm casually jogging," replied the master ninja.

"How can you be at the same rank as Gai Maito? He's much faster than you."

"You know Gai?"

"He tested me to reevaluate my abilities. He didn't use his forbidden technique, but we both removed our weights and he was as fast as me, although he hit like a fly."

Kakashi's eyes bulged.

"Gai hits like a fly? Without his weights?"

"Yeah, I barely felt it."

"Fun story, kid."

"Think what you want."

Sasuke and Sakura arrived at that moment. The introductions were uninteresting. The girl seemed to be eager to eat Sasuke, which rubbed Goku the wrong way. Sasuke was revenge-obsessed. Kakashi was uninteresting and barely said anything about himself. Goku said that he liked to fight strong opponents and to eat good food and that he wanted to become the strongest man in the world. Kakashi told them to meet him the next morning at 5 a.m.

X

After disrespecting them once more, Kakashi showed up three hours late to their exam. Son Goku had been exercising for two hours already and was hungry.

"Let's start this test so that I can go eat something," he stated.

Kakashi glared at him but explained the goal of the test. When he called the beginning of the genin exam, the other two scattered while Goku grabbed the bells.

"I've got the bells, does this mean I win?" he asked. "Can I go eat?"

Kakashi tapped his belt and felt nothing. He looked at Goku with the bells hanging from his hand and a bored expression.

"You…fail."

Kakashi proceeded to explain his dead comrade's philosophy that Son Goku partly agreed with – on the part about not leaving friends behinds. Then he tied Sasuke and Sakura to a pole and gave Goku two food boxes. He ran away after this and Goku started eating.

"You know, I think Kakashi meant that we were supposed to share as a team," commented Sasuke on a bland tone.

"Oh, you want some? Share the second box then, I've already finished the first one."

"Could you…please…untie us?" asked Sasuke between his teeth.

"Can't you break these ropes?" asked Goku, surprised.

"How do you want us to break ninja ropes?" asked Sakura, exasperated.

Goku used a chop movement and the ropes fell, cut clean.

"Like that."

Kakashi reappeared, but Son Goku had seen him come from far away.

"You…pass! Congratulations for helping each other despite the obvious level difference between the three of you. See you tomorrow at 5 in the morning."

He left. Goku looked at his teammates in pity and rolled his eyes.

"Okay. So our captain is a slow, weak shinobi who doesn't give a shit about you or me. I'm not a master, but how about I give you some training?"

Sasuke's eyes burned with excitement. He tried to hide it by stoically nodding his head, but it was obvious in his body language. Sakura seemed to hesitate.

"Sakura, you should say yes," declared Sasuke.

"Of course! If Sasuke wants to, then I'll do it too!" she exclaimed.

"Tomorrow, we'll find a field. I'll train you the same way I was trained."

"A field? What for?" asked Sasuke.

"You'll be weeding the field. Then making deliveries. Then escaping bee stings while tied next to their hive. Then you'll be swimming in a lake with a shark pursuing you."

"WHAAAT?! YOU'RE CRAZY?!" shouted the two genin.

"When you get used to it, you'll do it with twenty kilogram weights. Then with forty."

And in a loud complaint, team seven's nightmare started.