The central 'mystery' of the film is the identity of Seiji Amasawa, the boy who has checked out all of Shizuku's library books. The twist is that the boy who has been teasing her is, in fact, Seiji. His seemingly antagonistic behavior was his clumsy way of getting her to notice him, a fact he admits after they formally meet at his grandfather's shop. He reveals he had been checking out books hoping their paths would cross.
After two months of dedicating herself to writing, Shizuku completes her story, "Whisper of the Heart." She shows it to Mr. Nishi, who praises its heartfelt effort while acknowledging it's still 'rough.' This experience, though emotionally draining, solidifies her desire to continue learning and pursuing writing. She decides to focus on her high school studies to build a strong foundation for her future.
The film culminates in a famously sweet and abrupt ending. Seiji returns from his two-month apprenticeship in Italy a day early. He takes Shizuku on his bicycle to a lookout point to watch the sunrise. As the sun rises over the city, Seiji professes his love for Shizuku and asks her to marry him in the future, once he has established himself as a luthier. Shizuku joyfully accepts. This ending solidifies their commitment not just to each other, but to supporting each other's dreams, bringing the film's core themes to a hopeful and romantic conclusion.