Shinobu Okudaira, Akira Okudaira's older brother, is a university student defined by his constant vigilance toward his sister. He routinely uses his car for ferrying her around, a manifestation of his protective nature that often leads Akira to chafe under his persistent concern. Near the conclusion of Miwa Motegi's first year of high school, Shinobu enters a romantic relationship with her. This development introduces palpable tension for Akira, who navigates newfound awkwardness within their dynamic.