Moe Shinozaki is Yuu Shinozaki's older sister and the sole family member who comprehends his deep dissatisfaction with rigid societal expectations. She shares Yuu's passion for motorcycles, forging a unique bond within a family structure where parents and others disapprove of his rebellious mindset. When Yuu chooses to leave home on his motorbike, seeking freedom from conventional pressures, Moe actively facilitates his departure. She recruits her friend Tetsuo Kanda to assist Yuu with practical preparations for the journey, directly enabling his quest for self-discovery.

Her support continues beyond Yuu's initial departure. As he travels across Japan, Moe remains a concerned presence among the family left behind, reflecting her ongoing emotional investment in his well-being. She serves as a grounding presence who recognizes Yuu's fundamental need for autonomy, contrasting with others in his immediate circle, including his childhood friend Aoi, who fail to grasp his perspective. Moe's consistent role throughout the story is both facilitator of his journey and empathetic connection to his familial origins.