My Magic Box to Save an Empire

Modern girl Stella Sullivan travels to ancient times with modern supplies. She meets Regent Alistair Lawson, who is being assassinated. Using modern items, she resolves crises, helping the Young Emperor and solving court problems. They develop feelings. Stella opens the Time-Space Gate and returns to the modern era. Years later, they reunite in the modern world, confirming their fate, leading to a happy ending.