Age 762, planet earth.
It had been 6 years since Son Goku faced off and defeated the reincarnation of Evil at the finals of the 23th budokai tenkaichi. The hero of Earth was now living an idyllic life with his wife Chi Chi and their little son Gohan. The Earth was safe and at peace, the only potential threat was Piccolo who was training to defeat his rival, but a confrontation between the two would never come because fate had chosen a different course.
In an open field a farmer was working his land when all of a sudden something that looked like a small meteor crashed nearby, the man then took his trusted shotgun and decided to investigate. When he arrived at the crash site he saw a huge crater, he then took a good look at the meteor, but all he saw was a huge whithe ball. It was very strange he thought, but then the ball opened and out of it came a long haired man, the pilot of the space ship then started to levitate and faced the farmer who, in fear, pointed the shotgun at him.
"Why is this earthling still alive?" said the starman raising an eyebrow, he then activated a device that was on his right eye that started to make some strange sounds.
"Mh let's see, you have a power level of five? what the hell has Kakarot been doing on this planet" the tailed man yelled furious at his little brother for slacking at his work.
The farmer was in complete fear of the alien so he tried to shoot him, but the saiyan caught the bullet and sent it back to it's owner killing the farmer instantly.
The alien grinned and then activated his scouter again.
"Raditz here, I just landed on the planet but it seems that my little brother hasn't done his mission at all, I've detected many power levels this planet is still full of life, I will try to find Kakarot and report as soon as possible" Raditz then closed the call and started flying in the direction of the strongest source of power his scouter could detect.
On the other side of the planet Goku was training with his son, Gohan wasn't very interested in martial arts, and his mother wanted him to study so they didn't train much, but the boy still loved to spend some time with his father so he tried very hard to learn all that he teached him.
"So Gohan when you start a fight you should always put your hands together and bow your head in a sign of respect for your adversary" the saiyan said as he bowed, the boy copied his father movements and they started fighting, Goku went easy on his son because he was very young and didn't have much experience in martial arts. The fight started slow and on the ground but then their punches got faster as they moved into the sky. The art of flying was new to both of them, but Goku had already mastered it while his son was still trying to get better at it.
While sparring with his son Goku thought about one of the first opponents he faced that could fly: Tienshinhan. Years ago they had a challenging fight and Goku ended up losing against the crane school student in the final round 22th budokai Tenkaichi. Just a few months ago Tien and Chiaotzu went to train with Kami to get stronger, just like Goku did as a child after he defeated the great demon Piccolo.
"I want to fight him once again" Goku thought with a smile, the savior of Earth didn't know it yet but his lust for exciting battles was part of his very nature.
After a few minutes the little saiyan hybrid was tired so they flew down on the ground.
"You have improved very much Gohan, it won't be long before you grow stronger than me" Goku said to his son.
"Really dad?" the boy answered excited.
"Of course" Goku answered with a big smile on his face.
"Let's go now, we don't want Chi Chi to get worried".
"Flying nimbus" the saiyan earthling yelled and the golden cloud immideately appeared in front of them, they both hopped on it and flew away in the direction of their home.
Meanwhile in the desert Piccolo was meditating as his usual when all of a sudden he lost his concentration, with a horrified face he turned around, he had just felt an enormous ki presence that was approching his location.
"It's monstrous, this can't be Goku" the namekian thought, but in a second the source of that power was already in front of him, Piccolo looked at him shocked, it was a man with a tail around his waist and a strange black armour.
"Hey you are not Kakarot" the stranger said.
"Wait you are a... namek?" added Raditz with a shocked expression.
"I thought we had killed them all when we invaded their worthless planet" the saiyan thought.
"Namek?" was all that Piccolo could answer.
"You don't happen to know Kakarot do you?" the alien asked to the green man.
"No, who is that?" Piccolo said.
"Mh you are useless, I can't waste my time right now I will deal with you later" and with that the tailed alien flew away, Piccolo was left there speechless and with many questions he had no answers to.
"This is bad he is very strong, but if he thinks Earth is his for the taking then he would have to face me first" Piccolo thought as he flew in the direction of the stranger.
Goku and Gohan finally arrived at their home, but as soon as they jumped of the magic clouds Chi Chi was already at the door.
"Goku I already told you to not stay away for too long when you bring Gohan with you" Chi Chi said releived to see again her husband and son.
"Im sorry Chi Chi but we wer-" Goku's face immediately went pale.
"Goku what's wrong?" his wife asked thinking she had never seen his husband this scared.
"Go into the house and take Gohan with you" Goku said in a serious tone, but when Chi Chi was about to ask why a man came flying to their house and landed in front of her husband.
"Kakarot I have finally found you, mh you are the spitting image of our father" the stranger said with a grin on his face.
"Our father? Who are you?" Goku asked in a worried tone.
"What? Don't tell me you forgot about your big brother Raditz" the saiyan answered truly shocked and a bit disappointed.
"My name is Goku and I don't have a brother" Goku answered putting Gohan behind himself.
"Goku? Is this some kind of joke?" Raditz asked, but Goku stayed serious and on guard.
"Now I understand, you must have forgot everything, that's why you haven't completed your mission". Raditz said as he understood that Kakarot must have had some kind of accident that changed him completely.
"My... mission?" Goku asked.
"You are a saiyan, a member of the universe's strongest race, you were sent here to exterminate the population of this planet, I came here to fetch you so you could join our saiyan empire" the long haired saiyan calmly explained, Goku was shocked to hear his origins but this didn't change anything, he didn't care why he was sent here he was no saiyan he was raised on Earth and he wasn't a murderer.
"I'm not one of you, I maybe not be a human but I'm an earthling" Goku firmly declared turning down his brother's offer.
"Now leave this planet and never come back" he added.
Raditz was left spechless for a moment, this was the last thing he expected when coming to pick up his little brother.
"He is totally gone, what a waste of time" Raditz thought, deep down he wanted to meet his brother, but this Goku wasn't Kakarot.
"You are truly disappointing brother, if you won't join me" Raditz paused and looked at his nephew he then noticed his tail and a grin formed on his face.
"Your son will, even if he is a half breed he still has a saiyan tail and will serve our empire".
"My son and my husband aren't going anywere" Chi Chi screamed as she picked up Gohan in her arms.
Raditz grin turned into a laughter amused by the touching scene.
"Kakarot is this your women? you should teach her some manners" and in an instant the saiyan slapped Goku's wife away and she crashed in their house.
"You shouldn't have done that" Goku screamed while charging his brother, but the saiyan invader was much faster and kneed him in the stomach, Goku was now on the ground in pain.
Raditz then picked up Gohan who was now crying.
"Kakarot I will give you 24 hours to finish your mission, if you fail I will complete it for you but your child will end up as an orphan" after sending the ultimatum he flew away back to his space pod.
Goku was now recovering from his brother's attack, he got up still in pain and went to check on his wife, she was still alive but she was badly injured.
"If only I had a senzu with me" Goku thought. The protector of Earth then heard a sound and turned around, he saw Kami, Mr. Popo, Tien and chiaotzu on a magic carpet.
"I have seen and heard everything" said the guardian of Earth.
"You Tien and Chiaotzu must go to save Gohan I will take care of Chi Chi" the namekian added, but while they were talking another person arrived at Goku's house, it was Kami's evil half: Piccolo.
"You seem to be in a bad situation Goku" said the namekian mocking his rival.
"We don't have time for this now, we need to make a truce to face this invader" said Kami.
"Mh I agree if that alien kills everyone I won't have any slaves to torture once I conquer the planet" Piccolo asnwered with a smirk.
Goku called his magic cloud once more and hopped on it speeding away. The other three warriors followed suit and went to face this new threat.