Hanaoka is the long-serving head butler of the wealthy Nikaidou family. He is an elderly gentleman who has been in the family's employ for 45 years, having served since his master was a child. In his role, he is completely devoted to caring for Harunobu Nikaidou, a sickly but passionate professional shogi player and rival to the protagonist. Hanaoka’s primary motivation is the health and well-being of Harunobu, whom he has watched over and cherished for decades.

His personality is that of a kind and gentle old man, but his dedication to his charge can manifest in overly protective and slightly intrusive behavior. For example, he has been known to secretly monitor Harunobu's movements using a GPS tracker, a measure that goes beyond typical caretaking and shows the extent of his concern. He constantly worries about both Harunobu's physical condition and the results of his shogi matches.

Hanaoka’s key relationship is solely with Harunobu Nikaidou. He acts as a constant, stabilizing presence in Harunobu’s life, managing his environment and offering quiet support from the background. Within the story, his role is to provide a glimpse into Harunobu's privileged but sheltered upbringing, highlighting the efforts made to protect him due to his frailty. He does not undergo significant personal development in the narrative but remains a consistent fixture of support. One notable piece of information about his personal life is his favorite food, which is Mikazuki-yaki, a crescent-moon shaped cake from a local shop called Mikazuki-dou. His notable abilities include his attentive and meticulous management of the Nikaidou household and his unwavering, multi-decade loyalty to the family.