I often wonder how Future Trunks managed to retain his sanity.  In a world overrun by androids he is the Earths last hope.  He, and his mother Bulma, are the only 2 left from the original Z gang.  Future Trunks is 17 when we first lay eyes on him.  He does manage, however, to make quite an impression! 

Future Trunks shows up in a time machine built by his mother.

His first order of business is to defeat King Cold and Freiza who has managed to patch himself up again.  He slices and dices Freiza like nobody else imagined could happen. (And let me assure u that Future Trunks looked extremely hot doing it!)  Future Trunks talks a big game and comes through to deliver.  He is waiting for Goku to arrive back from his travels in space.  He is very vague with the Z gang and wont really tell them who he is.  The episode where he shows up is appropriately entitled “The Mysterious Youth”.  He ends up hanging out with everyone while they wait for Goku.  Bulma notices his Capsule Corp logo and presumes he is an employee.  Vegeta sees that Trunks keeps staring at him.  Vegeta thinks its because of the pink shirt. Future Trunks is actually just trying to see what his father is about.  He never knew him.  In Future Trunks timeline (also called the alternate timeline) Vegeta was not around to be a father and then eventually he died anyway.

Once Goku arrives he takes him to the side.  He powers up to Super Saiyan in an effortless motion, as does Goku.  They have a little display of power with each other (Trunks swings his sword around rather nicely and Goku blocks it with one finger).  After they power down, Future Trunks begins to explain who he is.  He advises Goku that he has come from the future so that  they may stop the androids.  He also explains to Goku that he (Goku) will develop a heart virus that will kill him.  Trunks gives Goku the antidote.  He starts to go into his heritage and Goku seems okay with Vegeta being his dad, he even manages to see a little resemblance.  Then when talking about his mother Future trunks points over to the Z gang.  Goku literally falls down laughing “Bulma is your mother!”  (One of my fav Vegeta lines is from this scene) Trunks explains to Goku that he can not disclose his parentage or else it may not happen.  He gets back into the capsule and goes back to work on the androids once again.  He never told the others who he was.

What kind of world does he return to?  A broken world.  As mentioned earlier everyone is dead. Future Trunks was very different than Chibi Trunks.  Bra never existed, Goten never existed.  His carefree life never happened – he always lived in the shadows and fought to protect the world.  He watched his best friend lose and arm and still manage to be a great fighter, but ultimately die.  He had no father to speak of. Everyday the world was destroyed a little more by the androids. Gohan had been his best friend and his mentor but he had seen Gohan's dead body before he ever came to our timeline to begin with.  Gohan had trained Future Trunks as best as he could.  Future Trunks was never able to reach Super Saiyan though.  He tried, he tried really hard, but it just wouldn’t happen.  Trunks did manage to use his rage and transform when he found Gohan dead at the hand of the androids.  Trunks took many beatings and defeats. And all of this by the age of 17.

He returns a few years later to help in the actual battle with the androids and Cell.  He has to save himself, as Chibi Trunks, and his mother Bulma from a crash landing.  Vegeta still wasn’t a good father. But it is his father and he wont let him die again.  Trunks does reveal himself to Bulma but it is by accident – he sees Vegeta flying off alone and mentions the word father before flying off after him.  Bulma figures it out.   He does end up revealing himself to Vegeta as well.

Future Trunks also trains in the Room of Spirit and Time and gets a little older and a lot stronger (and I dare say even hotter).  During his battle with Cell however he gets killed.  This causes a huge change for Vegeta.  Future Trunks is wished back to life by the dragonballs.  After that he returns to his own timeline and this time he is ready to defeat the androids.