Li Li. Role: A low-ranking court lady serving Shu Keigetsu. A mixed-race girl with a foreign mother (characterized by her red hair), she was discriminated against and treated coldly by those around her due to her origins. Achievements: After the body swap, she was the first to notice the change in Keigetsu (who is actually Reirin) and saw through her identity, exclaiming, "You are... Reirin-sama, aren't you!?" Other: She is a hardworking straight-man character who was moved by Reirin's overwhelming kindness and chivalry, swearing loyalty to her. Even after the truth was revealed, she chose to stay and support the real Keigetsu to rebuild the Shu-ku Palace rather than moving to Reirin's side.

Shu Gabi. Role: One of the Four Consorts (wives of the Emperor), known as "Consort Shu." Respected within the inner palace for her fair, beautiful appearance and gentle personality. True Nature/Motive: Her heart became twisted due to intense jealousy toward her former best friend, the Empress (Ko Kenshu), and past traumas, leading her to plot conspiracies that shake the inner palace. Actions: She incited Keigetsu's isolation and jealousy to make her perform the "body swap technique" with Reirin. She even disguised herself to torment Keigetsu (Reirin inside), acting as a very insidious and meticulous mastermind behind the scenes.

Ko Reirin. Appearance/Role: The protagonist, hailed as the "Prince's Butterfly" for her peerless beauty and intelligence, and deeply loved by everyone. Constitution: Extremely frail since childhood, growing up in an environment where she could have died at any moment. Essence: Because she survived a life of constant illness, she possesses an abnormally positive mindset and incredibly thick skin.

Shu Keigetsu. Role: The "true villainess" who was hated by those around her due to her strong inferiority complex and clumsy, blunt personality. Motive: Intensely jealous of the beloved Reirin, she used a forbidden technique to swap bodies and steal Reirin's "blessed position." Truth: She thought she gained Reirin's perfect body, only to be confronted with a "super-frail body that coughs up blood just by standing" and a hellish daily routine, falling into a panic of regret and confusion.

Ko Kenshu. Role: The Empress, the highest-ranking woman in the Kingdom of Ei, and the maternal aunt of the protagonist, Reirin (serving as a mother figure). Personality: An extremely intelligent and bold individual. While dignified, she has a relatable side, loving silly puns and having an unusually low threshold for laughter. Relationship with Reirin: The one who recognized Reirin's iron will despite her physical frailty and recommended her as the "Hime-jo" (Maiden) of the Ko family. She deeply trusts Reirin's unconventional mental strength and watches over her warmly (and sometimes broadly). (She knows about the body swap but chooses not to say anything.)

Shin U. Role: The "Chief of the Vulture Officers," the head of the security organization that enforces discipline in the inner palace. He is the half-brother of Crown Prince Gyomei, but because his mother was a foreign slave, he has no right to the throne and handles behind-the-scenes and dirty work. Appearance/Traits: A taciturn man who rarely shows emotion. He has beautiful jade-colored eyes inherited from his mother. Role/Appeal: Fair, cold, and blunt to everyone, but possesses a sincere and principled character. While investigating the body swap incident and palace conspiracies, he observes Reirin and Keigetsu's actions, serving as a key figure who provides precise support and leads the case to resolution from the shadows (ranking 4th in character popularity polls).

Ko Tosetsu. Role: The head court lady of the Ko family, serving as Reirin's personal attendant and bodyguard. She carries the blood of the Gen family, who excel in martial arts. True Nature/Loyalty: At first glance, she is a peerlessly cold "Ice Court Lady," but she is incredibly passionate inside. Initially, she found Reirin's daintiness insufficient, but after witnessing Reirin's terrifying "madness and effort" in training until she bled under the cover of night, she began to worship her from the bottom of her heart. Famous Line: Moved by Reirin's overwhelming mental strength and otherworldly positive actions, she often exclaims with sparkling eyes, "I, Tosetsu, am trembling with awe!"

Ei Gyomei. Role: The Crown Prince of the Kingdom of Ei, a perfect man excelling in both literary and military arts. He is Reirin's cousin. Personality: Sincere and responsible, but his love for Reirin is so deep it manifests as heavy, intense emotions. Actions: Immediately after the swap, he intensely hated and tried to ruthlessly corner the "villainess" (Keigetsu in Reirin's body) for hurting his beloved Reirin (actually Keigetsu in Reirin's body). However, after learning the truth, he deeply regretted his foolishness and began to do everything in his power to protect Reirin (and Keigetsu, whom Reirin cherishes).