First, Future Trunks says "Excuse me" as he slashes the opponent with his sword. Then, he slashes the opponent multiple times in rapid motions. Last, Future Trunks slashes the opponent with a large amount of force, inflicting a great amount of damage.
Future Trunks uses this attack during his brief sparring match with Goku in his Super Saiyan form. After both warriors transformed into Super Saiyans, Goku comments that he and Future Trunks look exactly the same. Future Trunks says "Let's find out" as he prepares to attack Goku with the first slash. Searching Future Trunks' feelings, Goku decides to stand still, knowing that Future Trunks will stop the attack. Promising that he will not stop, Future Trunks then attacks Goku with the rest of the slashes in the rush and Goku effortlessly blocks them with just one finger.
Appearances in games
Rapid Sword Stream was named in Dragon Ball Z: Ultimate Tenkaichi, where it is one of Future Trunks' Super Attacks in his base form. This rapid sword attack combo is called Stylish Buster in Super Dragon Ball Z, where it is also used by Ultimate Gohan. It is a physical attack called Multiple Sword Slashes in the Sword Master skill tree in Dragon Ball Online; this stronger variation of the Sword Slash skill can deal an additional 50% of its dealt damage when performed behind the target.