Mirai Shishiō, younger sister of Tsukasa Shishio, enters the narrative as a comatose patient sustained by life support after an accident at age six left her brain-dead. Her condition drives Tsukasa to fund her medical care through mixed martial arts, reflecting their unwavering sibling bond. A global petrification event later revives her stone form via a specialized fluid that repairs her brain injury, restoring her physical health. At 139 cm tall with blond hair and brown eyes, she dons an orange sleeveless dress accented by a dark blue ribbon, embodying youthful vitality. Her speech retains a Kansai dialect, rooted in her Osaka upbringing. Though her mental state initially mirrors that of a six-year-old due to stunted emotional growth during her coma, she matures gradually through engagement with the Kingdom of Science’s daily tasks and social dynamics. Revived, she reunites with Tsukasa, teasing his older appearance, and bridges his alliance with Senku Ishigami. When Hyoga betrays the group, Tsukasa shields her from attack, suffering critical injuries that lead to his cryogenic preservation. Mirai assumes oversight of his suspended animation, remaining in Japan as others voyage worldwide. Her growth intertwines with forging friendships—Suika and Ruri—and immersing in communal life, where she discovers a flair for fashion design. By the story’s end, she apprentices under Yuzuriha Ogawa, becoming a designer for a children’s clothing brand. At 18, she balances her career with playful grievances about Tsukasa’s intimidating reputation thwarting her romantic prospects, showcasing her blend of maturity and lingering adolescence. Her journey underscores familial devotion, resilience after trauma, and science’s capacity to reshape destinies, casting her as an emblem of renewal within the series’ exploration of humanity’s rebirth.