Trunks Story

In the future, Trunks is a teenager and Gohan is an adult. The survivors, Master Roshi, Bulma, and the others, spend their days hiding from the androids, who are still destroying everything they find. Gohan starts training Trunks to help fight the androids, but Trunks isn't able to reach Super Saiyan level.

Trunks and Gohan take on the androids anyway, but Trunks gets beaten senseless and Gohan loses an arm defending him. Gohan gives his last senzu bean to Trunks and nearly dies but for the intervention of Bulma. The two continue to train together and Trunks continues to be unable to reach Super Saiyan level.

Gohan goes to fight the androids again, alone, and gets utterly defeated. Trunks finds out what Gohan did, rushes to the scene, and finds Gohan lying dead in the ruins of the battle. Trunks is out of his mind with rage and finally becomes a Super Saiyan. He goes after the androids, but is still defeated, even as a Super Saiyan.

Bulma nurses Trunks back to health, and then gives him a time machine that she built with which he can return to the past, before Gokou's death, and give him some heart medicine to prevent his fatal heart attack. Trunks goes into the past, hoping to change the future that he lives in.