Kirio Yamada is a 17-year-old with violet hair and blue eyes, the older brother of Aoi Yamada. He adopts the alias surname "Yamada" during his search for his sister, a coincidence arising from its commonality in Japan, as Aoi also uses it as her false name. Kirio's quest begins after Aoi runs away from home following family conflicts, including an incident where he ate her favorite natto. He employs unconventional methods to locate Aoi, grabbing girls in districts where she was sighted under the assumption she might be disguised. This behavior fuels rumors labeling him a harasser. Despite his fierce dedication to finding his sister, Kirio frequently shifts focus, channeling intense enthusiasm into any task that captures his attention. As captain of his school's karate club, Kirio possesses significant martial prowess. He reflexively blocks violent attacks from androphobic waitress Inami Mahiru, attributing his defense to training. He misinterprets Inami's reactions as mere eccentricity and develops a crush on her, oblivious to her actual phobia. Kirio's persistence eventually leads to reconciliation with Aoi, though their relationship experiences a slow thaw. His mother, Kikuno Yamada, is a widow who initially struggles to connect with Aoi but remains a caring presence in their family.