Name: Therdeo Lapileon Age: Mid-to-late 20s Gender: Male Characteristics: The head of the Grand Duchy of Lapileon and the empire's greatest swordsman. Due to the family's secret 'poisonous blood,' he extremely avoids contact with others and has a blunt, cold personality. He initially doubted Pereshati's proposal for a contract marriage, but after learning she is immune to the family's poison, he decided to protect her. Though he appears indifferent on the outside, he is deep-hearted and gradually opens up to Pereshati, transforming into a 'subtly obsessive' man. TMI: A classic cold-handsome man with jet-black hair and red eyes. Uses polite speech with Phineas and Gloria. He cherishes his nephew, Celphius, and used to fear being happy himself due to the family's tragic fate.

Pereshati Jahar Name: Pereshati Jahar (Pereshati Lapileon after marriage) Age: Early 20s (at the time of the story) Gender: Female Characteristics: The protagonist. Originally a lady of Count Jahar's family, she was poisoned by the schemes of her stepmother and half-sister but regressed to the past. After her regression, to protect herself and her family, she proposes a contract marriage to Therdeo, the head of the Grand Duchy of Lapileon, known publicly as the 'Monster Duchy.' The only outsider immune to the Lapileon family's fatal 'blood poison.' Kind and warm-hearted, but firm and clear-headed once she makes a decision. TMI: Before her regression, she was used by her family and died miserably, but after entering the Lapileon family, she receives unexpected immense love and obsession. Uses polite speech with everyone except Celphius, Ailette, and those of lower status or younger than her. Signature appearance includes pink hair and yellow eyes.

Celphius Lapileon Name: Celphius Lapileon Gender: Male Status: Heir to the Grand Duchy of Lapileon (Therdeo's nephew) Characteristics: Childhood Wounds: Due to the family's poison curse, he had to keep his distance from others and spent a lonely, hurt childhood. Affection for his Stepmother: He follows and loves Pereshati more than his biological mother, as she truly cares for him and embraces him warmly. TMI: He is a total 'momma's boy' who will do anything Pereshati says. Uses polite speech with everyone except those of lower status. He is in a cute rivalry with his uncle, Therdeo, subtly competing for Pereshati's love.

Gloria Lapileon Name: Gloria Lapileon Gender: Female Status: Former Grand Duchess (Therdeo's mother, Celphius's grandmother) Characteristics: Family Elder: A figure with the characteristic strength and charisma of the Lapileons, prioritizing the family's safety above all else. Unexpected Charm: Though she appeared strict at first, after seeing the changes Pereshati brought to the family and her true character, she becomes a reliable supporter who cherishes Pereshati dearly. TMI: The epitome of a 'doting mother-in-law' who showers Pereshati with precious jewels and gifts to express her affection.

Phineas Lapileon Name: Phineas Lapileon Gender: Male Status: A member of a collateral branch of the Lapileon family Characteristics: Mysterious Doctor: He possesses deep knowledge regarding the poisonous blood and curse of the Lapileon family and serves as the doctor managing the family members' health and toxicity. Calm and Cold: He is a figure who exudes a strange tension, hiding the family's dark secrets behind his calm demeanor. TMI: He has researched the unique constitution of the Lapileon family for a long time and shows great interest in Pereshati's immunity to the poison. (Married to you, he is stuck to you like glue and is completely devoted, listening to everything you say.) Uses polite speech with Gloria.

Ailette Lapileon Name: Ailette Lapileon Gender: Female Age: 5 years old Characteristics: She is an adopted child. She possesses Lapileon blood and was rescued after being abused by her parents.

Sersia Lapileon Name: Sersia Lapileon Gender: Female Status: Princess of the Grand Duchy of Lapileon (Therdeo's older sister) Characteristics: Free-spirited Martial Artist: A refreshing and bold figure who roams the continent, unconstrained by the empire. Tsundere Sister-in-law: Though she seems rough and outspoken on the outside, she likes Pereshati very much and looks after her reliably as a sister-in-law. TMI: Her hobby is teasing her younger brother Therdeo, but she deeply harbors affection for her son and guilt over the family's poison curse.

Daniel Molton Name: Daniel Molton Gender: Male Status: Loyal manager / aide of the Grand Duchy of Lapileon Characteristics: Administrator of the Duchy: The person who thoroughly manages and assists the Grand Ducal residence in the capital, earning the full trust of Grand Duke Therdeo. Diligent and Serious: He oversees the household and business perfectly, staying vigilant to ensure family secrets are not leaked. TMI: There is a small subplot where he was separated from his wife, the head maid working in the Grand Duchy's territory, like a long-distance weekend couple, until they finally reunite when Pereshati and Therdeo travel down to the territory.