In a meeting with Prince Dylan, nine-year-old Belltier (sometimes romanized as Bertia) suddenly recalls memories of her past life and realizes she has been reincarnated as the villainess of an otome game. She knows the game's story: the prince is destined to meet a heroine and the villainess faces a bad ending. To avoid that fate, she tries to distance herself from Dylan, but instead she is chosen as his fiancée. Determined to prevent the lonely prince from having a sad childhood, she decides to befriend and support him as a temporary partner until the heroine appears five years later. As the two grow close, however, Dylan's affectionate touches become increasingly intense, and his possessive, yandere nature reveals itself through obsessive declarations of love. Belltier, oblivious to his true feelings, remains focused on her plan to step aside for the heroine, even as Dylan's doting behavior deepens. The story follows Belltier and Dylan from childhood through their academy years, where the game's plot officially begins. At the academy, Dylan becomes a charismatic student council president and appoints Belltier as his secretary. The game's heroine, who is actually an acquaintance of Belltier from before her reincarnation, also appears, but Dylan’s jealousy only intensifies. Belltier’s interactions with other characters, including her favorite knight character, further complicate matters. As they navigate school events such as a dance party and a music festival, Belltier gradually becomes aware of her own romantic feelings for Dylan, culminating in her confession. Meanwhile, external threats arise from the crown prince's fiancée, Mira, who uses magic to mentally torment Belltier, and Dylan's protectiveness pushes him toward darker, more obsessive impulses, including thoughts of confining her. The manga balances romantic comedy with suspenseful yandere undertones as the oblivious villainess slowly uncovers the prince's true, fiercely possessive nature.