Hikage Miyauchi is the middle child of the Miyauchi family, positioned between her older sister Kazuho and younger sister Renge. Born on December 7, she is a Sagittarius with O+ blood type. Her surname combines the characters for "temple, shrine, palace" (宮) and "inside" (内). She attended the Asahigaoka Branch School for her first eight years of education before moving to Tokyo for high school, where she lived in an apartment and returned to her rural hometown on weekends and school breaks. This relocation occurred after her father found work in another city, prompting the family to leave Asahigaoka. Hikage has shoulder-length dark violet hair and blue eyes, with an eye shape resembling her sister Renge's. Her hairstyle evolved over time; she once wore twin tails in her youth, later adopting a side ponytail to emulate a city girl aesthetic. On one occasion, she cut her hair above her shoulders during a festival. Kind and responsible by nature, Hikage strives to honor her commitments, though a disconnect sometimes appears between her promises and actions—such as failing to maintain contact with a childhood friend as intended. She craves attention and often boasts about her Tokyo experiences, attempting to impress others with her knowledge of urban trends, though these efforts are frequently met with indifference or comically overshadowed by Hotaru Ichijo's more authentic city familiarity. Despite this, she remains a well-liked member of her social circle and claims to have taught her friend Natsumi everything she knows about nature and the countryside. Her relationships define much of her life. She shares a strong bond with her older sister Kazuho, who cared for and corrected her in childhood. Her dynamic with younger sister Renge is complex; though Renge is often disappointed in her, they maintain underlying affection. Among friends, she is closely tied to Natsumi Koshigaya, often unintentionally participating in her antics, and she repeatedly attempts—mostly unsuccessfully—to impress Hotaru Ichijo. A significant figure from her past is Suguru Koshigaya, a childhood friend from whom she was separated after moving. In Tokyo, her main companion is Haruka Kudō, a classmate from the author's prior work "Little Devil's Meringue," with whom she shares an apartment. Hikage first appeared as a main character in Atto's manga "Little Devil's Meringue" (Koakuma Meringue) before being incorporated into this series. The author chose to make her Renge's sister because her surname had not been previously established and her eye expression closely matched Renge's.