Yotsuyu Hirasaka is a 15-year-old high school student associated with Narikozaka Manufacturing. Her name translates to "night dew" or "evening dew," reflecting a connection to nighttime moisture. She possesses pink hair styled to shoulder length, lilac-colored eyes, and stands 156 cm tall. Born on April 9 under the Aries zodiac sign, she has AB blood type. Her background reveals a notable transformation from a former delinquent lifestyle where she led the biker gang Crimson Glory. She successfully convinced its members to shift their focus from conflicts towards community service activities, demonstrating her leadership and positive influence. Within Narikozaka Manufacturing's group dynamics, Yotsuyu maintains a calm and collected demeanor. She becomes the object of admiration for newer recruit Nodoka Takahata, who experiences pronounced reactions like blushing or nosebleeds in her proximity, forming a recurring interpersonal thread. Yotsuyu participates in diverse scenarios including survival games, collaborative work at a themed café, hiking excursions, and the mock detective story "The Touka Shimoochiai Murder Case," which featured a segment from her perspective. She also appeared in a game show-style scenario alongside Nodoka. A significant moment involves her direct intervention to rescue Nodoka from a facility where Nodoka was subjected to non-consensual human experimentation involving electrocution and mind control techniques, securing Nodoka's safety. Yotsuyu navigates both everyday situations and extraordinary events without drastic personality changes. The narrative includes her presence in episodes focusing on festival preparations, outdoor training trips, promotional video productions, and lighter moments such as dealing with a toothache or community ghost stories.