The entire narrative of "Food Wars!" builds towards two major resolutions: Soma's relationship with Erina and his quest to surpass his father, Joichiro. The central antagonist for much of the series is Erina's father, Azami Nakiri, who takes over Totsuki and implements an authoritarian regime called Central, which dictates that all chefs must cook according to his specific 'gourmet' ideals. Soma and his friends form a rebel alliance and challenge Central to a "Régiment de Cuisine," a massive team Shokugeki. The rebels ultimately win, with Soma and Erina defeating the top two seats of the Elite Ten. Erina, having finally found her own culinary voice, becomes the new Headmaster of the academy.
The final season introduces a new antagonist, Asahi Saiba, a 'Noir' chef who wields cursed kitchen tools that can steal others' skills. A major twist reveals that Asahi is Azami's illegitimate son and therefore Erina's half-brother. He kidnaps Erina with the intent to marry her. This plotline culminates in the BLUE tournament, where Soma confronts and defeats Asahi. The final battle is between Soma and Erina. Although the result isn't explicitly shown, it's heavily implied Erina wins. However, in the process, Soma finally makes Erina admit his cooking is "delicious," fulfilling the promise he made in the first episode and breaking the final remnant of her mother's curse.
The ending reveals that the core of the story was never about Soma becoming the #1 seat, but about saving Erina from her past and her family's curse. His journey was the catalyst for her to heal and become a whole person. In the manga's epilogue, years later, Soma has traveled the world and returns to challenge Erina again, signifying their lifelong rivalry and partnership. The phrase Joichiro told Soma—that the best chefs find one woman they want to dedicate all their cooking to—is revealed to be the true theme, as Soma's entire journey was, subconsciously, for Erina's sake.