After returning to the past, Goku asks the Turtle Hermit to teach him the Mafuba, but…?!
Future Trunks sends Goku, Vegeta, and Bulma back to the past and faces off against Black on his own!
It’s a technique designed to seal demons away by sucking them into a container with a special Demon Seal on it.
For those wondering what the “Mafuba” its the Demon Seal or Evil Containment Wave that Master Roshi, Master Mutaito, and Tien use against Piccolo in the original Dragon Ball.