Mari Kusakabe is a 32-year-old motorcycle courier employed by Tiger Express and a central figure in the aftermath of the massive earthquake that strikes Tokyo. She is a single mother living with her young daughter Hina and her mother-in-law Reiko; her husband has passed away before the events of the story. On the day of the disaster, Hina has just turned four years old. Mari possesses a strong, instinctive sense of empathy and cannot ignore people in trouble, a trait that leads her to assist the lost siblings Mirai and Yuuki Onozawa almost immediately after the earthquake. When asked why she would help strangers, she answers simply that she does so because she is a human. Her personality is defined by a blend of caring warmth and practical resilience, allowing her to act as a stabilizing force in the chaos that follows. Her primary motivation throughout the story is twofold: to reunite with her own daughter and mother, who were in Sangenjaya, and simultaneously to fulfill a promise she makes with Mirai and Yuuki to guide them safely to their home in Setagaya. This dual responsibility creates an internal conflict between her intense anxiety for her own family and her commitment to protecting the children in her care. She provides essential survival skills and emotional stability for the group, drawing on her familiarity with the city and her calm demeanor under pressure. Her role in the narrative is that of a guardian and surrogate maternal figure to the Onozawa siblings, particularly as Mirai matures through the ordeal. Her relationship with Yuuki is marked by a protective trust; he comes to view her as a reliable adult. With Mirai, she serves as a mentor, helping the initially cynical teenager develop a greater appreciation for family and life. Key relationships also include her co-worker Aya Kawasaki, who checks on her welfare, and her daughter Hina, whose safety remains the driving force behind Mari’s perseverance. Over the course of the journey, Mari struggles with moments of despair, especially when faced with the possibility that her family may not have survived, but she ultimately proves her selflessness and strength by continuing to press forward. Her development highlights the balance between personal desperation and altruistic duty, and she emerges as a figure who embodies both human vulnerability and uncommon courage. Notable abilities include her competence as a motorcycle rider, her knowledge of disaster response—such as navigating ruined streets, locating aid stations, and managing limited resources—and her capacity to maintain composure and offer reassurance in the most harrowing circumstances.