Dragon Ball Z Special 2: Zetsubou e no Hankou!! Nokosareta Chousenshi - Gohan to Trunks
English name: Dragon Ball Z: The History of Trunks
Genres: Adventure, Drama, Fantasy
Type: Special, Episodes: 1
Aired: Feb 24, 1993
Studio: Toei Animation
Source: Manga
Rating: PG-13 - Teens 13 or older
Synopsis:
It has been thirteen years since the Androids began their killing rampage and Son Gohan is the only person fighting back. He takes Bulma's son Trunks as a student and even gives his own life to save Trunks's. Now Trunks must figure out a way to change this apocalyptic future. 

(Source: ANN)