The Villainess Who Only Had 100 Days to Live Had Fun Every Day

Lelouché, a duke's daughter, was pushed down a flight of stairs by someone and was transported to another space. There, she meets a "god-like being" who tells her that her fiancé has been unfaithful to her and that she will die in 100 days. She knows that she can avoid the worst of it, but not escape death, and she begins to try her best to die beautifully in 100 days.