Characters you would find within the One Piece Baratie Arc are the Straw Hat Pirates: Monkey D. Luffy, Roronoa Zoro, Nami, and Usopp; influential ones like Sanji; Chef "Red-Leg" Zeff; Patty; Carne; Don Krieg; Gin; and the famous swordsman Dracule Mihawk. This arc consists of Episodes 19 to 30 in the anime and Chapters 42 to 68 in the manga. This arc is mainly formed as a result of the need of a cook for the Straw Hat Pirates. The setting is an ocean-going restaurant in the shape of a fish somewhere in the East Blue, known as Baratie.
The arc starts with the arrival of the Straw Hat Pirates into the Baratie looking for a chef to recruit into their crew. Their arrival is concurrent with that of Marine Lieutenant Fullbody, who was dining in the same restaurant. An argument breaks out as Fullbody insults the food and all the chefs in the restaurant, pitting him against sous chef Sanji. In the process, Luffy damages the Baratie and, to pay that off, works as a chore boy for a year. This arc introduces the concept of culinary pride and the importance of not wasting food—themes central to Sanji's character development—while Luffy struggles with his new role, often causing more harm than good.
Things get interesting with the arrival of Don Krieg, accompanied by his pirate armada. The latter, dying of starvation, and weakened due to a wretched encounter in the Grand Line, he comes mainly to the Baratie for food. Sanji does not work on the principle of giving up food to those who are hungry, as other chefs refused to feed Krieg. He is betrayed in his act of good will as Krieg tries to hijack the Baratie once rejuvenated. The battle erupts into a war between the chefs of Baratie and Krieg's pirates.
This arc focuses on Sanji's past, particularly his relationship with Zeff. Apparently, it was Zeff, the "Red-Leg" pirate, who saved Sanji one time from a forgotten rock they were left on, where he sacrificed his leg to eat so that Sanji could live. It seemed that from this experience, their bond grew very strong, and this instilled in him a great respect for food and cooking.
Finally, the story arc comes to a head when the world's greatest swordsman, Dracule Mihawk, makes his unexpected appearance, and after tearing up Krieg's fleet in the Grand Line, he finally tracked them down to the Baratie for a confrontation, which puts him in a duel with Zoro, who wants to take his title. Although this battle ends in defeat for Zoro, it turns out to be a real turning point because he vows never to lose again and to redouble his commitment to becoming the world's greatest swordsman.
The battle against Krieg's forces continues, but Luffy confronts Don Krieg by himself. It is a fight between Krieg's weapons, dirty tricks, and Luffy's raw, straightforward fighting. At the same time, Sanji has a fight with Gin, Krieg's loyal subordinate, while testing both fighting skills and convictions.
The victory of Luffy over Don Krieg and the defeat of his pirate crew close out the Baratie Arc. More importantly, this is the beginning of Sanji joining the Straw Hat Pirates. After much unwillingness to leave the Baratie in the first place, feeling that he still owed a great debt to Zeff, he was encouraged by him and the other cooks to realize his dreams: finding the All Blue, a fabled ocean where all fish from the world come together. This decision brings into Luffy's crew not only a good cook but also a character with a very strong and rich backstory and ideals, further enriching the dynamic of the Straw Hat Pirates. It is an important point in the series, as it expands on the crew and deepens the relationships between characters, setting the stage for further Grand Line adventures.