Subete wo Ubawareta Oujo wa Kishi wo Matsu

Irene lives a life of luxury as a princess in a wealthy and peaceful country. Out of curiosity, she sneaks out of the castle and meets Ivy, a girl from the slums who looks just like her. Due to certain circumstances, the two switch places for a short time, but this ends up igniting Ivy's ambition to escape her impoverished life. Irene loses her status and place to herself to Ivy, who pretends to be the princess, but with her natural good nature, she gradually overcomes her difficulties. Meanwhile, the only person in the castle who feels uneasy about the swapped Ivy is Leonardo, a palace knight who reveres the princess, and sets out to search for the real Irene.

(Source: ebookjapan, translated)