Masamune Makabe, a once-overweight boy, was cruelly rejected by a wealthy and beautiful girl named Aki Adagaki during his childhood. Humiliated by her harsh words, Masamune vowed to transform himself and exact revenge by making her fall in love with him, only to reject her in return. Years later, Masamune has become a handsome and fit teenager, adopting the name "Masamune" as a symbol of his new identity. He transfers to Aki's school, determined to execute his plan.

At school, Masamune quickly gains popularity, but Aki, known as the "Brutal Princess" for her sharp tongue and disdain for men, remains aloof. Masamune begins his scheme by attempting to charm her, but his efforts are complicated by Aki's unpredictable behavior and her loyal maid, Yoshino Koiwai, who seems to know more about Masamune's past than she lets on. As Masamune gets closer to Aki, he discovers that her harsh exterior masks insecurities and vulnerabilities, challenging his resolve to carry out his revenge.

The story introduces additional characters who further complicate Masamune's plan. Neko Fujinomiya, a wealthy and eccentric girl, develops feelings for Masamune, creating a love triangle. Meanwhile, Masamune's childhood friend, Tae Futaba, reappears in his life, adding another layer of complexity to his relationships. As the narrative progresses, secrets about Masamune's past and Aki's true feelings begin to surface, forcing him to question his motives and the validity of his revenge.

The series explores themes of self-improvement, identity, and the consequences of holding onto past grievances. Masamune's journey is marked by moments of humor, drama, and introspection as he navigates the challenges of his plan and the evolving dynamics of his relationships. The story builds toward a climax where Masamune must confront the truth about his feelings and decide whether his quest for revenge is worth sacrificing the possibility of genuine connection.