Future Gohan is the alternate timeline counterpart of Gohan that appears in the timeline in which Future Trunks lives. He is showcased as a twenty-three year old man, and is depicted as the mentor of Future Trunks. In the original manga, he appears in a special chapter titled "Trunks The History - The Lone Warrior", and he made his anime debut in the Dragon Ball Z episode "Ghosts from Tomorrow" during one of Future Trunks' flashbacks. He would receive a much larger role a short time later in the television special,Dragon Ball Z: The History of Trunks.
Future Gohan appears as a tall, stern, and muscular man (considerably more so than the appearance of his main timeline counterpart during the Majin Buu Saga). He also dons a uniform greatly resembling that of Goku's early uniform, and states that he is inspired to wear his "dad's old colors" in the hopes that he will one day be as strong as he was. The only differences between his uniform and Goku's is that the sleeves are longer on his, his boots are a dark blue with yellowish stripes on the bottom edges and without the line running in the middle of the boots from top to bottom, and he also wears his own kanji symbol on the back, Han, 飯. Bulma even states that Gohan looked strikingly similar to Goku when wearing this uniform. His hair is cut much shorter, somewhat resembling the haircut his alternate past counterpart had when fighting with Cell, only it was more grown into (because Future Gohan was a full-grown adult). He also obtains a scar that runs down the left side of his face, the after effect of an injury sustained during a battle with the androids.
Due to the apocalyptic world that he spent the latter half of his life in, Future Gohan is shown being very serious and more aggressive than his present timeline counterpart, but does retain his calm and joking nature, much like his father. Future Gohan is shown to be in quite a bit of pain and stress after all the years of challenging the androids alone, and has a sort of "do or die" attitude.
However numerous times he appears to hide it, let go, and just enjoy life for what it is worth, most notably when telling Trunks to forget about becoming a Super Saiyan until he knows he is ready (in the anime special). Future Gohan also calls Trunks his little brother ("bro" as well in the FUNimation dub), as the two appear to be incredibly close, and Gohan appears to think of him as a little brother.
Future Gohan also seems to be deeply angered by the deaths of his close friends, which is told out loud to Trunks by stating that he remembers back to how the androids killed Piccolo and Krillin when transforming into a Super Saiyan.
Because Future Gohan presumably never went to school and became a scholar, it is assumed he spent all of his time training and pondering ways in which to stop the androids, making him a complete warrior instead of the scholar his present timeline counterpart becomes in late Dragon Ball Z and in Dragon Ball GT.
However, he is never able to receive the ample training with Goku like his present timeline counterpart does, and therefore, is never able to reach anywhere near his full potential, which leads to miserable defeats against the weaker Androids of the future.
Earth's Final Hope
The point of timeline divergence with Future Gohan and his main timeline counterpart occurred when Future Frieza arrived on Earth in August of Age 764. Originally, Goku uses his Instant Transmission technique to arrive and kill Future Frieza and his father (Goku even states to Trunks in the main series that was what he was going to do), but the events in the series differ, as Future Trunks arrives and kills the tyrants instead of Goku, thus the timeline divergence. Future Gohan hails from the true original timeline (one without Trunks coming back in time, obviously) and because of this, the events that unfold are far different from those in the main series.
After the death of his father due to a lethal heart virus in Age 766, and then the murders of the Z Fighters by the androids on May 10th, Age 767, Gohan's life is altered drastically. It is presumed that these events are what first sparked Gohan's transformation into a Super Saiyan, but it is never truly shown.
Over the course of the following thirteen years, Gohan trains himself to be able to kill the androids, and over time, develops a close relationship to Trunks, the son of Vegeta and Bulma. As the last remaining Z Fighter, he continuously takes it upon himself to challenge the androids, even though he is outnumbered and outclassed. Gohan becomes a Super Saiyan sometime during the years-long struggle against the androids. In the special, Trunks also states that being a half-Saiyan hybrid like himself, Gohan must understand how he feels about not being able to stop the Androids, and while he does, Gohan still states that Trunks is currently an emotional wreck like he was when he was not allowed to train and fight with his friends.
Future Gohan's first true appearance in the special is his arrival at a city the androids had just recently attacked, thirteen years after the Z Fighters had been killed. He encounters Trunks in the ruins of the city, and after hearing his plea to learn to fight, agrees to take him under his wing.
One day, during a day of relaxation, the androids attack the theme park Super World while Gohan and Trunks happen to be flying overhead. The two quickly head toward the park to battle the androids. Upon arrival, Gohan instructs Trunks to stay out of the fight. Gohan then battles with Android 17, transforms into his Super Saiyan form and despite a few lucky hits from Android 17, quickly gains the upper-hand. However, Android 18 soon intervenes and Gohan finds himself quickly overwhelmed. In an attempt to assist Gohan, Trunks rushes in only to be quickly defeated by Android 18.
However, before Android 18 can deliver a powerful energy blast to the young warrior, Gohan rushes in and takes the attack for him, saving Trunks' life. Gohan then carries the unconscious Trunks while trying to find a place to hide. He is successful in hiding until the androids decide to bomb the entire area in hopes of driving them out. Gohan manages to protect Trunks and stay hidden, but at the cost of his left arm, which is completely blown off in the bombing.
Luckily, Gohan has one Senzu Bean left, and is able to give it to Trunks, which saves him from death. Trunks awakes a moment later and brings the unconscious Gohan back to Capsule Corporation where Bulma treats his wounds. After Gohan's injuries heal, the two resume training. Trunks, pushing ever closer to becoming a Super Saiyan, quickly begins to improve day by day.
The End Of A Hero
During a day of training, the nearby Pepper Town is attacked by the androids. Gohan prepares himself for battle, only to see young Trunks begging to fight along side him. Gohan seemingly accepts, only to knock Trunks out to avoid the young warrior from being nearly killed again, or worse. The one-armed Gohan seals his final fate when he flies into the city alone and ambushes the androids. Despite his handicap, Gohan puts up a long, suspenseful fight against the combined power of the androids.
As Gohan tries his hardest to keep his defenses up, he is ganged up on and knocked down into the city streets below, before the androids launch energy blasts like a machine gun from the sky, killing him outright. Trunks awakens when his mentor's energy depletes. He then searches the city, only to find Gohan's dead body laying in a pool of water. His rage bursts out and he transforms into a Super Saiyan for the first time.
- It is to be noted that in the manga chapter upon which the special is based, not only was the first battle against the Androids (where Gohan obtains his facial scar and severed arm) never shown, but Trunks was already able to transform into a Super Saiyan, and Android 18 never joins the battle, as Android 17 mockingly brags that he only used under half of his maximum when he defeated Gohan over a year ago, and kills him with ease before Trunks is able to awaken and find Gohan's corpse in the debris (also notable is that no rain is ever seen during this scene, although Trunks ramming his fists into the ground in frustration is shown, if much less accentuated)