Keizō Nonomiya is Jun Nonomiya's father, married to Toshie Nonomiya. Together they run a family restaurant, which Jun utilizes to deliver food offerings to Zero as a strategy to capture his attention and affection. Keizō functions as a steady, reliable parental presence within the household and their culinary business. His consistent role supports the domestic environment enabling Jun's inventive activities and school life, without documented personal conflicts, expanded narrative arcs, or details on his background or development.