In a kingdom where the Great Saint who governs the Great Clock Tower is revered, Duke Veronica is declared a Great Saint candidate and forced into an engagement with Crown Prince Derek, a man she despises. The only condition that would allow her to cancel the arrangement is to awaken her dormant Great Saint abilities before her eighteenth birthday. With the help of her childhood friend and second prince Edzel, Veronica trains tirelessly under the current Great Saint, Basia, but the trials are severe and progress is slow. Adding to her distress, rumors spread that Baroness Flora is the true Great Saint and that she is engaged to Edzel, leaving Veronica feeling cornered.

At the academy graduation party, just before she turns eighteen, Derek publicly announces the dissolution of their engagement, declaring his intention to marry Flora instead. Far from being devastated, Veronica is overjoyed—this is what she has been working toward for years. Derek does not realize that Veronica is the genuine Great Saint and that Flora is an impostor. With the truth exposed, Edzel confesses his long-held feelings and asks Veronica to marry him.

Now established as the true Great Saint and engaged to Edzel, Veronica balances her sacred duties with her new role as crown princess. She faces trials including a possessive and overwhelming affection from Edzel, political maneuvering from the queen mother who opposes their union, and a ceremony known as the spring festival. When the former Great Saint Basia goes missing near a border town and a researcher named Yuzzek also loses contact, Veronica investigates alone and is pulled into a hidden passage in a temple. Learning of her disappearance, Edzel takes up a legendary gear and vows to find her, launching a determined search.

The story weaves fantasy and romance as Veronica navigates the responsibilities of sainthood, the schemes of those who wish to harm her, and a deepening bond with Edzel.