100-nichi Go ni Shinu Akuyaku Reijou wa Mainichi ga Totemo Tanoshii.

Duchess Lelouche is told by a divine voice that she will die in 100 days. Her engagement to the Crown Prince is in trouble, as he is preoccupied with other women. Despite knowing her fate, she cannot prevent her death but is told she can influence how it happens and its consequences. She makes a deal: if she lives the remainder of her life well, she asks for a reward in the afterlife. With this in mind, Lelouche begins taking actions to support her family and uncover the forces working against her that will ultimately lead to her death.