Sennya Senshoku Monogatari

Erendira, the "shame" of the royal family of the small country of Lenze, is the child of a king and a slave. Abandoned by her father, she is abused by her half-siblings every day. In the cold winter, Erendira is pushed into a pond and finally dies. Then, her memories of her previous life as a Japanese person come back to her, and she vows to "kill all the royal family!" and starts a new life! However, that day, Lenze is destroyed by the great power Agdnigur, and the royal palace becomes a sea of blood overnight. The angry emperor declares that all the people of Lenze will be slaves, and when he gathers the royal family in the king's chamber, he declares that he will behead them all on the spot. "I'll let anyone who is useful live," the emperor boasts, but the royal family begs for their lives and their heads are chopped off one by one. When it's her turn, the emperor asks her, "So? Are you incompetent or competent?" Erendira clearly answers, "Your Majesty! Would you like some pudding?"