Prime Minister Saburōta Negishi serves as the maternal uncle of Shū Koibuchi and holds honorary uncle status to Kuranosuke Koibuchi, Shū's half-brother. As Japan's Prime Minister, he conducts high-level governmental meetings, including policy manifesto discussions with officials like the Minister of Health, Labor, and Welfare. Privately, Saburōta exhibits a markedly unserious and eccentric personality, especially around family. He gravitates toward gossip and displays exaggerated excitement over trivial matters, such as fixating on a woman's hairstyle during a televised broadcast. His behavior shifts dramatically when alone, experiencing "wah wah wah" moments of distress, though he quickly recovers upon encountering stimuli like fashion or gossip. Physically, Saburōta possesses black hair and eyes, but experiences significant hair loss, earning him the nickname "Kahlkopf" (bald head) among family and colleagues; he insists his hair remains "nine percent present." Married, Saburōta verbally celebrates attractive women, though this behavior remains superficial. He shares a close, unconventional bond with Kuranosuke, affectionately calling him "Kura-pyon." His interactions with Kuranosuke involve intense enthusiasm for the latter's cross-dressing, often manifesting as frenetic, gag-like behavior that contrasts his public image. He occasionally displays similar exuberance toward Shū but prioritizes Kuranosuke. Saburōta participated in a publicity event with "Miss Peanut," discussing topics from ecology to family to bolster his media image as Prime Minister. After the event, he contacted Kuranosuke via text, indicating familial affection. His appearances are documented in the anime episode "Enchanted" (Episode 3) and the manga debut in Volume 1, Chapter 4.