Miori Sanada is a classmate of the protagonist, Kokoro Anzai, at Yukishina Number 5 Junior High School. She serves as the class president, a position that gives her social influence among her peers. Her role in the story is that of the primary antagonist in Kokoro’s everyday life, as she is the instigator of the bullying that leads Kokoro to become a shut-in. Miori’s motivations for targeting Kokoro stem from her infatuation with a boy named Chuta Ikeda, who attended elementary school with Kokoro. Kokoro speculates that Miori believes Chuta has feelings for her, and as a result, Miori orchestrates a campaign of psychological harassment to drive Kokoro away. Her method includes manipulating Chuta into telling Kokoro that she is ugly and that he does not like her, an act calculated to hurt Kokoro deeply.

Miori’s personality is marked by jealousy, cunning, and a willingness to use others as tools to achieve her goals. She does not directly confront Kokoro but instead works through a third party, which suggests a degree of indirectness and social manipulation. She appears confident in her social standing as class representative, yet her actions reveal underlying insecurity about her place in Kokoro’s life or in the affections of Chuta. The narrative shows no dimension of remorse or development; Miori remains a static figure of cruelty who serves as the catalyst for Kokoro’s traumatic withdrawal from school. She does not participate in the events of the castle, nor does she interact with the other main characters in a meaningful way. Her significance lies entirely in the real-world pain she inflicts, which frames the central conflict of the story. No notable abilities are attributed to her beyond her capacity for social manipulation.