In the future, he arrives on Earth and goes on a rampage, leaving humanity on the brink of extinction. He encounters Trunks and easily defeats him. Trunks survives their encounter and, for one year and half, prepares to travel back in time using a Time Machine with Bulma in an attempt to save the future. Trunks and Bulma are eventually intercepted by Gokuu Black himself when the villain kills Bulma and destroys their hideout. Trunks narrowly escapes with enough fuel for a one-way trip back to the past while Gokuu Black pursues him. Gokuu Black appears again and attacks Mai and taunts Trunks.

(Source: Dragon Ball Wikia)