The small country of Adarshan has been conquered by the Castoria Empire. To secure a new border alignment and cement an alliance between the two nations, the victorious Adarshan general Alexid Deke Adars, the king’s younger stepbrother, is forced into a political marriage with Castoria’s sixth imperial princess, Justinia. There is one complication: Justinia is only ten years old.

Set in a fantasy kingdom reminiscent of medieval Europe, the story primarily unfolds within the Adarshan court. Alexid, known on the battlefield as the Black Demon and despised by many for his illegitimate birth and brutal prowess, is a lonely and isolated figure. Justinia arrives as a child bride, initially stubborn and resentful. She blames Alexid for indirectly taking someone important from her, and their early relationship is marked by conflict and mutual wariness.

As the narrative progresses, the political machinations of a faltering monarchy come to the forefront. The king, Alexid’s older stepbrother, appears hostile but may have hidden reasons for keeping his distance. Justinia gradually sees past Alexid’s fearsome reputation, recognizing his loneliness and genuine kindness beneath the cold exterior. Their relationship evolves from enmity into a tentative friendship and deeper affection, though the romance remains gentle given her age. Meanwhile, Alexid must contend with court conspiracies and the weight of his own past, while Justinia begins to mature and carve her own place in a foreign land. The story includes supporting characters such as Yuuze Ricks, a trusted ally, and figures like Fred and Samuel who influence the court dynamics. Over nine chapters and two volumes, the manga balances its light romantic and dramatic elements with the political tensions of a kingdom struggling to hold together after war, culminating in a resolution that focuses more on the stability of the realm than on the romantic relationship alone.