Anastasia is the eldest daughter of the noble Shaderan family and the older sister of Marie, the series' protagonist. In stark contrast to Marie, who is treated as a servant by their parents, Anastasia is the family's shining star and receives their full affection and attention. She is described as having a princess-like appearance, which contributes to the initial misunderstanding when Count Kyros Granado, captivated by Marie, accidentally proposes to Anastasia instead.

Behind her privileged facade, Anastasia possesses a resourceful and creative personality, maintaining a secret passion for making clothes. This hobby is not recognized or approved by her strict father, forcing her to work on it in secret, and she had even considered opening a clothing shop in the royal capital as an alternative to a conventional marriage. She is also a loving and deeply caring sister who worries about Marie's wellbeing, showing a sensitivity and compassion that contradicts her outwardly perfect image. Despite being the favored child, she is not unkind to her mistreated younger sister.

Anastasia's role in the story is dramatically set in motion by a tragic event. While traveling to marry Count Kyros following the mistaken proposal, her carriage is sabotaged and swept away by a river. She is declared dead since her body was never found, which is later revealed to be a deliberate lie by a corrupt coachman to cover his crime. In truth, Anastasia survives the attack and escapes. This event is the catalyst for Marie being sent to Kyros's estate as a replacement bride, forming the central premise of the series.

After her disappearance, Anastasia is taken in by a blind button craftsman named Smith Norman in the royal capital's artisan district. To remain hidden and protect herself, she adopts the male name Arthur and helps Smith with his work, taking advantage of his inability to see her true identity. Her key relationships evolve from this new life; she develops a unique bond of trust with Smith Norman, who aids her despite his own limitations. Later, when Kyros visits Smith's shop to fix a wedding ring, Anastasia discovers that Marie has married Kyros in her place.

Anastasia's motivations are driven by love and protection for her sister. Haunted by negative rumors that portray Kyros as a cold, eccentric, and harsh tyrant, she becomes deeply worried for Marie's safety. This concern compels her to take the significant risk of sneaking into the Granado ducal household to check on her sister. During this infiltration, she encounters Marie and Kyros and learns the truth, clearing up the misunderstandings born from wild gossip. She discovers that Kyros is not the monster the rumors described, allowing her to find some resolution.

Regarding character development, Anastasia demonstrates remarkable adaptability and resilience. Despite losing her standing and facing mortal danger, her ingenuity and quick thinking enable her to not only survive but also forge a new life and identity for herself while continuing to look out for her loved ones. Her journey is one of being burdened by her parents' expectations to be a perfect doll, only to have that life stripped away and be forced to rely on her own hidden strengths. She is cautious and resilient, capable of adapting quickly to dangerous and unexpected situations.

Notable abilities include her exceptional skill at making clothes, a talent she has honed in secrecy. She is also highly adaptable and a quick thinker, which proves essential for surviving the attack on her carriage and navigating her new life under an assumed identity. Her compassion and worry for her sister directly fuel her most significant actions, such as her risky infiltration of Kyros's estate.