The DBS manga introduced a new character named Black Goku, who tampered with the time barriers to attack Universe 7. Dragon Ball Super Manga is illustrated by Toyotaro but Akira Toyirama oversees the entire plot. Akira is also the writer of the original dragon manga series, which is considered the most popular of all time.
In the fourth volume of the DBS manga, there was an interview with Akira Toyirama, who talked about the inspiration for Black Goku. This character was introduced in the Future Trunks Saga. Akira said that Black Goku was inspired by Copies of the Heroes, characters like Fake Ultra Man and Kamen Rider Black. It becomes a perfect opponent against Goku and Vegeta being able to fuse. This gave the writers an opportunity to introduce Vegito in the series once again.
Here, Akira is referring to the genre called tokusatsu . It parodies famous cartoon shows and movies in live-action form with extremely special effects. One of the famous series, Kamen rider, features such fake warriors against heroes. The plot of Kamen Rider Black and Future Trunks has many similarities.
Black Goku was originally a Supreme Kai named Zamasu, who stole the body of the current Goku using the Super Dragon Balls. He then threatens to wipe out the entire universe with Zamasu in the future. Having been a god for a long time, Zamasu developed a hatred for mortals and the gods who protected them. He wants to rebuild the entire multiverse after destroying all the universes.
Akira sought to expand Dragon Ball’s story in this new series. He kept the flashy themes and intense fights from his original work. To borrow ideas from a comedic live-action and make it as sensational as possible, he needed someone like Goku. The character has been widely accepted since he was introduced as being on par with SSG Blue in power.