I Became the Villainess in an Anticlimactic Novel

Reading I Became the Villainess in an Anticlimactic Novel manhwa, I Became the Villainess in an Anticlimactic Novel manga with alternative name:  I Became a Villainess in a Deadly Novel / 용두사망 소설 속의 악녀가 되었다 / IBVIAAN with Description: I became the villainess of the novel I was reading, but that novel… had just about the most anticlimactic ending imagineable. After a long and slow romance development, the empire was suddenly destroyed by a demon on the wedding day of the male and female lead