As a quiet, book-loving noblewoman, she was always unfavorably compared to her flashy twin sister and shunned by her family. Her miserable life takes a terrifying turn when her sister seduces an engaged prince and is punished with an order to marry the rumored Reaper Duke, a terrifying man whose wives always die mysteriously. To protect his favorite child, their cruel father forces her to take her sister's place as a substitute bride. With no way to escape, she prepares for her doom and marries the duke. However, to her utter surprise, her new husband is a perfect gentleman who continuously saves her from danger. Why is such a genuinely kind man known as the Reaper Duke? What begins as a deadly sacrifice slowly blossoms into a sweet and mysterious romance!