Maria Kurose is a supporting character in the story. She is introduced as a transfer student who joins the same class as the main protagonists, Ryuuto Kashima and Runa Shirakawa. She is the fraternal twin sister of Runa Shirakawa, though the two were separated after their parents divorced during elementary school, with Maria staying with their mother and taking her surname.

Her background reveals that she was Ryuuto Kashima’s first crush in middle school, but she rejected his confession, an event that left a lasting emotional mark on him. When she reappears, she initially presents herself as a sweet and innocent girl, quickly attracting attention from other male students. However, her outward demeanor hides a more calculating and cold side. Maria struggles with deep-seated insecurities stemming from her parents’ divorce, particularly the feeling that her father chose Runa over her. This unresolved pain drives her to want to be the most favored person and fuels a rivalry with her sister. She deliberately tries to undermine Runa’s relationship with Ryuuto, spreading negative rumors and attempting to create conflict.

Despite this, her actions stem from a place of hurt rather than pure malice. Over the course of the story, she is confronted about her behavior and eventually apologizes, beginning the process of mending her relationship with her sister. Her development involves recognizing her own insecurities and learning to let go of her grievances. She does not possess any special abilities; her role is primarily that of an antagonist turned conflicted figure, whose actions force the main couple to confront challenges and grow. Her key relationships are with Runa as her estranged twin and with Ryuuto as a former crush who has moved on. Through these connections, she evolves from a source of tension to someone taking steps toward reconciliation.