Shinitagari no Oujo

Wendy was born as the daughter of a concubine in the Kingdom of Leverze. Just a week later, when it was announced that the queen was pregnant, the entire nation rejoiced—and Wendy's existence was forgotten. If she hadn't regained the memories of her past life as Yukino, she might have given up on living altogether.

Sixteen years passed, and one day, the king received a demand from the Allied Nations: "Send us a capable princess to become a prince's bride." That's when he suddenly remembered—"Come to think of it, aside from my lovely princesses, didn't I have one more daughter...?"

This is the story of the forgotten youngest princess, who was offered up as a substitute for the demanded royal bride. She vows to destroy the homeland that sold her out, and go out in a blaze of glory.

(Source: Shousetsuka ni Narou, translated)