Happy New Year, Second Brother and Sister-in-Law!

After the vampires' great calamity, their numbers dwindled until fewer than one in ten remained. The Council of Elders decided to force matches on their thousand-year-old bachelors to strengthen the pureblood ranks. Smith Nian, the most notorious turncoat in vampire history, was matched with the eldest son of the Augustine family on her thousandth birthday. The next day, she heard that her fiancé had been laid to rest for good. Nian Xiajiu: ??? A car, a house, no father or mother. What could be better than being a newlywed widow?! Still, the Augustine family gave her a grand wedding. The man, covered in smoke and blood, hurriedly married her without even changing out of his suit. As he slipped the ring onto her finger, he gave her a smile that might have meant anything and greeted her: "Please take good care of me, sister-in-law." The woman was alluring, yet heartless. She was his dear big brother's wife. Nian Xiajiu felt a chill run down her spine: ...It was as if some enormous predator had its eyes on her. Then the little bat, acting on instinct, got into a fight with the big bat and tore the castle apart. The underlings: "Second Brother and Sister-in-Law...they're so close..." Augustine Yate, second-in-command of the underworld and a vampire at the very peak of combat prowess, finally understood after surviving explosions, tsunamis, and enemy attacks: "My dear sister-in-law is very serious about trying to kill me." "But I still love her." He discovered that his love was unspeakable, hidden from the light, impossible to put into words. "Every day, my heart is scorched by holy fire." Nian Xiajiu glanced at him coldly: Second Brother, what are you thinking? Hurry up and drink this bottle of poison. Yate: ...Hah. According to the butler, the second master and the lady of the house got into another fight that night. The noise carried on all night. They're so close! (They really were just fighting!) A gentlemanly scoundrel x a heartless little thing. The male lead handles the romance, while the female lead handles the career. A vampire at the peak of combat prowess x a vegetarian godmother and turncoat. They love to fight and fight because they love each other (the order is correct). Modern setting, with an underworld. A fake sister-in-law: she never actually married the elder brother. Theme: Everyone is equal, monsters are equal, and humans and monsters are equal.