Douyara Dareka no Kaiki ni Makikomareta You desu

Irene has been the acting queen for 20 years, single-handedly managing the country's political affairs while her warmongering husband, King William, was away at the front. The day after she finally ends the long war and is about to hand over all administrative duties to the returning king and take a long-overdue rest, she suddenly wakes up in a strange bed. When she looks in the mirror, she finds herself 20 years younger, back in time, on the day before the tea party where she was chosen as the crown prince's fiancée.She is shocked and furious to learn that the twenty years of her life she gave to the state have been undone. Realizing she was caught in someone else's regression, she decides to do things differently in her second life. She refuses to become the crown prince's wife, determined to live a life of leisure. However, in her place, her beloved younger sister is chosen as the new crown princess, setting the stage for a new and unexpected future.