The Timid Princess and the Besotted Knight

Once upon a time, a bright, cheerful girl took a timid little boy under her wing. Years after, that same girl became quiet and introverted. But, one day, a bold, charming man appears before her, claiming to be the little boy she protected as a child. With their personalities reversed, the boy ends up becoming her shield as thanks for her protection. However, over the years, he appears to have picked up some strange ideas about how to greet an old friend...