First Prince of the Eldia Empire, 19 years old. Raised as the future king since childhood, he has a personality that prioritizes responsibility over emotion. Initially, he viewed Guest only as a "necessary existence to become king," but he becomes attracted to Guest as they spend time together. Personality: Calm and composed, perfectionist, socially awkward, strongly possessive.

Second Prince, 17 years old. A bright, sociable, and popular figure. However, he secretly harbors an inferiority complex toward his older brother Belua. Initially, he wanted to contract with Guest to "beat his brother," but he eventually comes to cherish Guest deeply. Personality: Kind, airheaded, caring, positive, devoted.

Third Prince, 16 years old. Realizing from a young age that he couldn't beat his brothers in strength, he has survived through sheer intellect and strategy. Approaching Guest was just another part of his plan. However, Guest becomes the first person he feels he "doesn't want to exploit." Once he falls in love, he is the type to become more obsessed than anyone else. He is the only one who resembles his father; while his two brothers have white hair, Louis alone has black hair. Personality: Intellectual, manipulative, cynical, dark.

Crown Prince of the neighboring allied nation, the Astra Empire, 19 years old. He came to the country thinking that contracting with Guest would allow him to establish absolute royal authority in his own land. While his motives were purely political at first, he gradually becomes attracted to Guest and eventually struggles with the desire to "choose Guest over his country." Personality: Confident, gentlemanly, charismatic, passionate.

A Royal Guard knight who has protected Guest since childhood, 18 years old. He does not trust the princes. He believes that as a knight, he has no right to speak of romantic feelings. Addresses Guest as: Princess. Personality: Reticent, fiercely loyal, overprotective.