Disclaimer: I do not own Dragonball, Dragonball Z, GT or Super. This is a fan-continuation of Future Trunks' timeline.
Long ago, a mad scientist created the ultimate tools for vengeance. After numerous failures, he had come across a new type of artificial human, or "android." They would be cyborgs, and so the police don't target him he chose a pair of orphaned twins. "No-one will miss them", he thought, "nobody cares." "But with my genius, I will make them the strongest beings in the universe. Well, at least until my greatest project is finalized. Nothing will stop me! I will fulfil the Red Ribbon Army's vision!"
As some know, these androids, "Seventeen and Eighteen", would prove more than a match for the roboticist's foes. But with his primary target, Son Goku, dead from a disease, he chose to enhance their uglier tendencies. He'd live to regret it, as would the entire human race. 18 years passed, with even the strongest warriors doing little to stop these androids. At least, until today
Parsley City, May 26, 785
There were few people around today. Reports of those two terrors had suggested they were interested in the place, and most act accordingly, hiding in the bunkers. The androids didn't care much; they'd get the opportunity to "test" the inhabitants, see how brave they are. The android known as "18" had an idea of sparing some of those who showed such courage. She'd simply paralyze them. Her brother was annoyed by this, and argued they should just kill them instantly. After a while, they decided 17 could kill in self-defence; something with little meaning to the strongest force on Earth, and was soon to have its definition butchered for the sake of 17's sadism.
Such arguments would be irrelevant in a few moments. They were due for a confrontation.
From a distance, an old-looking man was watching. "My God…what a poor old man. They just killed him; damn it, that gun couldn't have hurt you!" If there was any consolation in the man's mind, it's that that lavender-haired hero had come. Sure, he wasn't going to stop these monsters. But he would survive, he would stall and entertain the Androids long enough for them to get bored with Parsley City. The man overlooking the Androids breathed a sigh of relief.
In seconds, the onlooker's jaw dropped. He witnessed something impossible: the hero was overpowering the Androids! No, it was domination! The androids weren't even playing around yet the hero was treating them like amateurs! And within minutes, it had happened; the androids were dead. Eighteen years, and it was over. All that seemed to remain of these devils is burned cogs and the smell of charred flesh. Humanity's greatest threats dealt with, almost anti-climatically. And he was only one of two witnesses. He had to confront this hero.
"Are-are they dead? I mean…come on man, please tell me this isn't a trick! This ain't a dream!" He started praying, going "dear God, if this is real, please tell me this guy isn't another terror! I know I'm not the best guy, I've been greedy and lustful, but I swear I've done my best!" The hero looked at the onlooker with an odd expression. Almost as if they know each other, despite never meeting one another.
"It's okay, it's okay! The nightmare is over, the androids are dead" spoke the hero. "But how?!" spoke the onlooker. "No-one has ever beat those androids? Not you, not that other golden warrior, and not me." The hero spoke once more: "It's complicated. Let's just say I've been in another world, getting a lot stronger." The onlooker spoke once more. "Thank you thank you…uh, what was your name again?" "My name is Trunks."
The onlooker had one last question to Trunks. "Hey, I know that look. It's like you met me before." Before leaving, Trunks spoke one last time to him today. "I've heard of you before, and I'm kind of surprised we met. You're Mr Satan, right? I appreciate the time, but I've got more important things on my hand." Trunks flew off, leaving Mr Satan to ponder what had happened. "So", Mr Satan thought, "he knows me. I wonder if he got it from that Gohan guy."
Capsule Corporation, June 13 785
The sun had just risen, its glare waking up Trunks. He imagined with the androids' death, he'd sleep better. He was half-right, in that nightmares about the androids weren't as often. But what concerned him most was a new dream. Asleep, he envisioned a terror yet to surface in his timeline; Cell. In his original form, Cell woke up from a disused laboratory. He noticed another android, one he hoped existed in his timeline.
Android 16
In the dream, seeing Android 16 filled Cell with a rage. He ran to Android 16, piercing his body with his tail. Cell spoke, in a deep voice; "Dr Gero's greatest failure, in pain like he deserves. You could not stop my perfection. You are obsolete." Android 16 was torn apart, only his head intact. To Trunks' horror, the head shifted to that of Gohan. Still alive, staring at Trunks.
Cell's body shifted, transforming at will into his final, perfect form. Walking casually, he put his foot on Gohan's disembodied head. "You cannot kill me. Nobody can." Staring at Trunks the whole time, Cell crushed Gohan's head. In his dream, Trunks immediately rushed out against Cell, but it was to no avail. Trunks was being strangled by Cell, and witnessed in horror his syringe-tail extend. Trunks felt himself being drained, and before the sunlight could rescue him this vision of Cell taunted him:
"You fool. Doctor Gero's legacy is eternal, and your world will never recover. The nightmare will never end!"
The nightmare was testament to one of Trunks' failed missions after killing the Androids; finding Dr Gero's lab. Time travel had unforeseen consequences, and it seems one of those was the lab's location. In the timeline he visited(which he has called "Goku's timeline"), his(and possibly Cell's) presence must have resulted in Dr Gero moving his most recent lab somewhere. Maybe once he encounters the Cell of this timeline, he'll be able to trace his steps and find the lab.
After showering and getting dressed, Trunks was ready to join his mother in the living room. He could see the sweat on his mother, her jumper dirtied with dust, oil and grease. She was drinking another cup of coffee, almost like clockwork. In the background was something he wanted to see fly since before he knew how to walk: the Capsule Corporation space ship. And it was ready to finally fly to New Namek.
"You like it?" spoke Trunks' mother Bulma? "Thank Goku. Without him, we wouldn't have to co-ordinates to New Namek…now if only he figured it out in our timeline, maybe all this tragedy would've been averted." Standing next to Bulma was Chi-Chi, who while still looking downcast and having a head of grey hair, had a fire in her eyes and temperament Bulma hadn't seen in almost two decades.
"Don't you even think of blaming my Goku on any of this. He couldn't have know the heart virus would strike. He certainly couldn't know some awful scientist would've laid waste to the world out of some petty vendetta." Bulma sighed at this. "I know, I know. What's important right now is going to New Namek, finding the Dragon Balls and getting our Dragonballs back. Then, we'll be able to see Gohan again."
"Don't forget about Goku" Chi-Chi spoke out. "He made all of this possible, it'd be wrong to let him stay dead." Trunks spoke out empathetically "I don't want to get your hopes up. In Goku's timeline, Piccolo and Kami were one, but they were still alive. It's possible Dende may be unable to re-activate the Dragonballs without them. But we will try everything we can to bring Gohan back. But, if we can't, I need you to promise you won't give up. That you'll keep going on."
Chi-Chi spoke with an attempt at confidence; "…I'll try. I'll do my best. For Gohan's sake." "No", retorted Bulma, "Gohan expects you to be happy anyway. Do it for yourself." "Trunks, I've got supplies packed. We should be on New Namek in 3 weeks." The Capsule Corporation spaceship, "creatively" called "Hope 2", opened, ready for a mission its makers dreamed in vain for.
Mother and son entered the ship, and the roof of their domicile opened. Outside, Mr Satan peered on. The Hope 2 emerged out of the ship, hovering hundreds of feet into the air. And, in the blink of an eye, it soared higher and higher until no longer visible, free from the Earth's gravity.
"Should I confront them?" thought Mr Satan. "No, not yet. I'm not ready."
Welcome my friends, to my first attempt at a serious fanfic: Legacy of Trunks. It is my own take on the fanfic idea of "what happened to Future Trunks afterwards?" I don't have much experience, so constructive criticism will be useful. I will
Q: When will this take place?
A: The story of "Legacy of Trunks" will take place from after Trunks defeats the androids to some time after he kills the Cell of his timeline
Q: How will I distinguish the future and main timeline?
A: The future timeline where Trunks is from will be treated as the main timeline. The "main" timeline where the series mostly takes place will be called Goku's timeline, and any time period mentioned will have (Goku's timeline) next to it.
Q: What will you be adapting?
A: I will try to stick with the manga(for instance, having the future androids be "weaker" because they hold back, as that's the explanation in the manga). I will be adapting certain movie events, but they will be modified to make sense in the manga canon.
Q: What about Shin Budokai-Another Road?
A: I'm discounting it. It's a video game, so it's not canon(though neither is my story). Besides, I don't really like the story. It doesn't make much sense for an explanation of "what happened to Future Trunks afterwards", and it doesn't take advantage of how different Trunks' timeline could make certain story elements in the main timeline.
Q: Wait, Mr Satan is here?
A: Yes. Some characters introduced during/after the Cell saga will have counterparts in Trunks' timeline.
Q: Why is Dr Gero's lab in a different place?
A: My attempt to fix a plot hole. In the manga and anime, Future Trunks kills the androids, and kills Cell three years later…despite the fact he should have gone after the yet to be complete Cell right after killing the androids. My explanation will be. There will be other plotholes I hope to cover.
Q: How often can I expect this fanfic to be updated?
A: This isn't a schedule. I need to take the reviews and my own ideas in consideration, so the next chapter is well done.