The core of this episode—and the Enies Lobby arc as a whole—is Luffy's realization that his current strength was insufficient to keep his friends safe.
How Did Luffy Figure out how to use Second Gear? : r/OnePiece 273 : Everything Is to Protect My Friends! Seco...
" Everything Is to Protect My Friends! Second Gear Activated! " is the pivotal title of of the One Piece anime. This episode marks one of the most iconic turning points in the series, as Monkey D. Luffy debuts his Gear Second transformation during his battle against Blueno at Enies Lobby. The Motivation: Protecting the Crew The core of this episode—and the Enies Lobby
: Luffy’s crushing defeat by Admiral Aokiji earlier in the series served as a wake-up call. He realized that to face the world’s strongest powers, he needed to evolve so "no one has to go away". Second Gear Activated