Upon receiving the white marriage declaration, I remembered my past life. I will keep an observation diary.

Salvia, the daughter of a marquis, is declared to have a "white marriage" with only her memories from her past life to rely on, and is coldly told by her husband-to-be, Marquis Alphonse, that she should simply "attend evening parties and serve as a decoration." With time on her hands, Salvia begins an "observation diary" in which she meticulously records the spending habits and behavior of her husband's mistress, Clarice――.