Revenge of the Vampire Ex-Wife

Quick answer: 4 episodes, English original audio, and episodes 1–4 play right here tonight.

The pure-blood vampire duchess Lydia is reborn during a blood moon, returning to the eve of her wedding, when she was murdered by her husband Sebastian and sister Beatrice. Using her memories of her past life, she orchestrates a scheme that exposes their plot to seize the dukedom and kill her. After the trial, Beatrice is banished, and Sebastian becomes a blood slave. Lydia discovers a secret letter revealing that the two families have a blood feud dating back three hundred years, stemming from the murder of their ancestors' lovers, and that Sebastian's revenge has a reason.

She reveals the long-buried truth, abolishes the blood slave system, and releases Sebastian, who chooses to stay and atone for his sins. Beatrice returns aged, repents, and dies, while Elder Marquez, who concealed the past, loses power. The two put aside their generations-long hatred, their feelings for each other grow, and they finally hold their wedding during the blood moon, completely resolving the feud between their families and reconciling with the past.