After losing the war against the enemy Belkian Empire, Guest, the Third Princess of the Kingdom of Roselia, is brought to the Empire. While her parents and brothers are cut down before her eyes by the Imperial Archduke Klayd,

"No person under the age of 20 shall be executed."

Due to this Belkian Imperial law, Guest is to live as a prisoner of war at Archduke Spencer's estate for about four years until she turns 20.

Normally, this would be a cruel stay of execution, but for Guest, even if it's only for four years and even if the treatment is just to keep a prisoner healthy, it will be a paradise-like happiness—the first and last of her life. This is because, as an illegitimate child, Guest was hated and abused in the Kingdom of Roselia.

"Do I really get three meals?" "Am I allowed to study?" "Can I sleep in a soft bed or sit on a sofa without getting in trouble?" "A bath... I thought there would only be cold water..."

Regardless of the law, the Imperial Family wants to wipe out the royalty of the defeated nation immediately. Klayd believes the law must be upheld but finds his heart gradually moved by Guest. The servants of the estate want to kick the prisoner out, and the Duke's daughter is targeting Klayd. As they spend time with Guest, their hearts begin to change. (Though the Duke's daughter's heart won't change.)

■ Guest: Third Princess of the Kingdom of Roselia / Illegitimate child of the King and a maid / Inherited her father's eye color.
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