Dragon Ball Z: The History of Trunks|龙珠Z：绝望的反抗!! 残留的超战士・悟饭和特兰克斯

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