Shimako Toudou, a reserved and elegantly poised student at Lillian Girls’ Academy, ascends from petite sœur to Rosa Gigantea after Sei Satō’s departure. Her tranquil presence, marked by a porcelain complexion and mid-length waves of light brown hair, evokes comparisons to a delicate antique doll, concealing a contemplative spirit wrestling with vulnerability. Beneath her composed exterior lies a fear of emotional bonds transforming into suffocating “shackles,” a hesitance rooted in her fragmented upbringing.

Born to a former Buddhist monk and a woman destined for Catholic vows—whose union defied both faiths—Shimako faced early loss: her mother died postpartum, her father succumbed to illness soon after. Raised by Buddhist relatives, she navigated a silent clash between her family’s traditions and her childhood resolve to pursue Catholic vows. At twelve, her declaration to become a nun led to a compromise: enrollment at Lillian, a Catholic school testing her devotion.

Initially resolved to depart for a convent, Shimako’s path bends through bonds with Sei and Noriko Nijou. Reluctant to lead or accept a petite sœur, she retreats into supporting roles, wary of her capacity to nurture without constraining others. A transformative phone exchange with Noriko before an Italian trip fractures her defenses, reframing Lillian as a protective “nest” rather than a prison. This awakening emboldens her to embrace Noriko as her petite sœur, signaling her tentative acceptance of interdependence.

Quietly perceptive, Shimako voices empathy where others overlook it—notably advocating for Yumi Fukuzawa’s autonomy during Sachiko Ogasawara’s Yamayurikai recruitment. Her introspective depth intertwines with a reverence for nature: she collects ginkgo seeds and cherishes cherry blossoms, a legacy from her father nurtured by her uncle. These quiet passions mirror her evolution from solemn isolation to measured openness, balancing self-contained reflection with the fragile courage to forge enduring ties.