As any fan of One Piece will tell you, the main protagonists of the Straw Hat Crew are practically fueled by the power of friendship. The long-running 1000-plus episode anime series adapted from the Eichiiro Oda manga follows Monkey D. Luffy. As a plucky young pirate with the ability to stretch his body, he aspires to set sail across the treacherous ocean to discover the fabled "One Piece" treasure and become the Pirate King. To that end, he assembles his own motley pirate crew.
Named after Luffy's signature headgear, the Straw Hat Pirates become one of the most infamous pirate crews in the world over the course of the series. Not only that, they've become inseparable as friends with nigh unbreakable bonds.
Of course, that certainly doesn't mean that those bonds haven't been put to the test before. In fact, many of the Straw Hats have left the crew before to deal with harrowing personal matters, including Sanji. Why did he leave the crew?
Why did Sanji leave the crew in 'One Piece'?
Vinsmoke Sanji is one of the earliest recruits in Luffy's crew, having been scouted as the Straw Hats' chef. Not only is he a beast in the kitchen, but his kick-based martial arts skills make him a considerable fighting force when taking on some of the most dangerous threats that the seas have to offer.
As all of the Straw Hat recruits over the course of the series, Sanji trusts Luffy with his life. That's what made his departure so impactful.
In a betrayal that Toei Animation themselves considered equivalent to Judas betraying Jesus Christ in the Bible (no, that's not a joke), Sanji once left Luffy and the Straw Hats behind as he left to deal with a personal matter.
In the Whole Cake Island Arc, Sanji is reunited with his estranged and abusive siblings of the Vinsmoke Family. He is informed of his unwitting betrothal to one of the daughters of Big Mom, one of the most dangerous pirates in history.
After his fellow Straw Hats are threatened by the combined might of the Vinsmokes and Big Mom, Sanji agrees to go through with the marriage in order to protect his friends. He leaves the crew and even faces off against Luffy to drive home his departure.
Of course, the Straw Hats themselves don't give up on their friends that easily. Once they learn the truth about Sanji's apparent betrayal, it isn't long before they resolve to convince him to return to the crew.
What episode does Sanji rejoin the crew?
After overcoming some harsh battles, Luffy reunites with Sanji who reveals to his friends the true reason behind his having left. Sanji even tearfully admits that what he really wants to do is continue his pirate life with the Straw Hats.
Though it took a while for them to reunite, it isn't long before Sanji and the Straw Hats come together once more with the purpose of crashing Sanji's own wedding and continuing their adventures.