Ruko Ayase

As Yuuto's older sister, this character serves as a private secretary to a company president and possesses a high level of martial arts skill, holding the rank of 2-dan in karate. Despite being a diligent worker, she has a rough demeanor and often speaks bluntly, leaving household chores to her brother. Due to her parents' frequent absence, she naturally assumes the leading role in the household alongside her brother. Her initial reaction to meeting Haruka was one of pleasure, a feeling that surprised her brother.