I Will Become the Ex-Wife of the Beast

After transmigrating into a 19+ novel as Bella—the younger sister destined to face disaster when her older sister has an affair—she decides to step in and marry the terrifying Grand Duke in her sister’s place. Her true plan is to safely secure a divorce along with generous alimony to build a wealthy, comfortable life. However, the cunning and dangerous beast of a Duke has no intention of letting her go so easily.