Here are the specific details regarding the debut:
Before Episode 726, Luffy and Trafalgar Law were pushed to their absolute limits by Donquixote Doflamingo. The Heavenly Demon's "Birdcage" was rapidly shrinking, threatening to slice the entire island of Dressrosa and its citizens to pieces. luffy 4th gear episode
To win, Luffy needs a new form—one that combines the speed of Gear Second with the power of Gear Third, but without the drawbacks. Here are the specific details regarding the debut: