Tamamori Betty

"On that night, I became the cursed monster's bride—" Stella, the eldest daughter of the Viscount Quinwitch, though she was adopted, lived happily with her kind family. However, one day, Stella's younger sister Lilinette was chosen as the "Monster's Bride". Once a century, a cursed monster confined to a castle requires a sacrifice, so Stella resolves to go there in place of Lilinette. And there, she meets the monster - a bloodstained vampire named Lavi.

She is about to turn 30 years old. Just when she thought her marriage was going smoothly at, her boyfriend cheated on her on the day of her birthday and she was thrown into the bottom of her life. On the way home from the wedding, she was crying because she was so fed up with herself that she couldn't even be happy for her friend's happiness, when her business partner, Ren Isshiki, appeared...Waka thought that a boy too young for her was out of the question. A love story about an older female office worker who dreams of a safe marriage, but is charmed by, dropped by, and doted on by a younger man.