Mikuni Katou is a student at Itan Private High School, first encountered during the first-year field trip to Kyoto. Her brown hair is styled in circular braids, and she wears distinctive circular glasses, usually seen in the standard school uniform. Reflecting her family's affluent background, she often wears a kimono at home; they reside in a large, traditional Japanese-style mansion featuring elements like a black toilet. Her mother is Yakuna Katou, maiden name Sewa. Mikuni learned shogi from her grandfather, a former professional player who still supports her training, fueling her serious ambition to become the first woman to compete equally with male professionals. She demonstrated notable skill by reaching the semifinals in the Women’s Phoenix Shogi Tournament. Grouped with Shouko Komi and Ayami Sasaki via lottery during the Kyoto trip, Mikuni prepared a detailed itinerary covering temples, Universal Studios Japan, and Nara’s Deer Park, eager to ensure the perceived "class idol" Komi enjoyed herself. This rigorous schedule caused minor friction with Sasaki over a lack of relaxation time. Komi defused the tension by sharing photos expressing her enjoyment, leading Mikuni and Sasaki to see Komi as a relatable peer. This shared experience forged a strong friendship among the three. Later, on the train ride home, Sasaki tricked Mikuni into sitting beside Makoto Katai, whom Mikuni had admitted interest in due to his "sharp eyes". Following the trip, Mikuni and Sasaki became inseparable best friends, frequently hosting "girl talk" sessions at Mikuni’s house. These evolved into regular parties where they, Komi, and others like Rumiko Manbagi and Kiyoshi Isagi discussed romantic developments. Mikuni applied shogi strategies to analyze relationship dynamics, deducing secrets from minimal clues. Her fascination with romance directly impacted her shogi performance; during a critical tournament match, she felt stuck until receiving a telegram from Sasaki about Komi and Hitohito Tadano holding hands. This news energized her, leading to a decisive victory, establishing a recognized pattern linking romantic topics to her competitive focus. Academically, Mikuni excels, ranking 16th out of 150 students in her second-year summer term finals. She served as class president for Class 2-2. Her interactions extend beyond her core group; she taught shogi strategies to Tadano and Komi, though their differing approaches once caused a brief disagreement. Mikuni’s personality blends seriousness and responsibility with a playful, easily flustered side regarding romance, often responding to embarrassment with light shoulder punches. Her hobbies include reading the manga "From Today, This Is!!" – whose tough protagonist reminds others of Katai – and enjoying strawberry daifuku. She placed 21st in the series’ popularity poll.