One Piece is a story where even the most simple of arc-exclusive identities can make an impact, and nowhere is that more true when you see Usopp's arc in Water 7. The sniper of the Straw Hat Pirates also started off as a relatively weak liar, and even after joining he realized that his place in the crew could very well be invalidated due to his insecurities and weakness. Which is why when that came to a boil against Luffy, he not only disrespected his captain, but left the crew for a while. One Piece isn't shy about showing why Usopp's insecurities prevented him from returning and properly facing his mistakes.