Twenty-five-year-old Eri, nursing a broken heart, takes her first overseas trip to Italy. After being pickpocketed and left alone and stranded, she is rescued by a handsome Japanese man named Jinnō, who turns out to be a billionaire. The two share a magical, passionate night together, and although they part ways the next morning with only a note left behind, Eri returns to Japan unable to forget him. Three months later, a fateful coincidence brings them back together in Tokyo. They begin a whirlwind romance, and Eri is slowly drawn into Jinnō's world of staggering wealth—helicopter travel, exclusive parties, and lavish gifts. She struggles with the vast difference in their backgrounds but is deeply loved and protected by him at every turn.

The story follows their relationship through a series of romantic, occasionally tense, narrative arcs. A famous fashion designer named Maurice, an old friend of Jinnō’s, challenges him for Eri’s affections. A mysterious threatening letter arrives, forcing Jinnō to take Eri to a secluded estate where she meets a man from her past. The media later picks up on their relationship, causing a scandal that threatens Jinnō’s reputation. Overwhelmed by the pressure of living in such a different world, Eri decides to leave Jinnō, but his devoted secretary convinces her to return. After they reconcile, Jinnō’s company is bought out by his estranged older brother, who initially seems hostile. Eri accepts a position as the brother’s secretary to help bridge the gap, and through her efforts, the siblings eventually make peace. The narrative culminates in a proposal, a wedding, and a honeymoon, ending with the couple happily married, having weathered the obstacles that came from their clashing worlds.