姫君は騎士団長 (Series) favorite_border

[DeepL Translation - needs review] Volume 1 Introduction: Christina, the head of the prince's Kingsguard in the Kingdom of Roborovs, has grown up as the prince's best friend and a man. One day, Prince Leonard asks her to pretend to be his fiancee for the sake of the kingdom, and she reluctantly agrees... The princess life of the kingdom's most powerful knight begins.

(Translator: DeepL)