Ritsuko Takahashi is the head teacher of class 5-2 at Doumori Elementary School, renowned as the school's beautiful, unmarried "madonna." She approaches her teaching duties with serious dedication and a strong commitment to her students' welfare and education. However, she experiences pronounced anxiety and fear regarding supernatural phenomena, especially spirits and yōkai, which frequently appear at the school. This fear often causes her to react violently toward Meisuke Nueno (Nube) when he discusses or presents evidence of such entities.

Her dynamic with Nube evolves significantly. Initially, she views him primarily as a nuisance due to his supernatural preoccupations and his attempts to attract her attention with supernatural displays, which she consistently rebuffs. Over time, witnessing Nube's consistent efforts to protect students and others gradually builds her courage in facing supernatural threats. This shift leads her to develop romantic feelings for him, contributing to a love triangle involving Yukime, a yuki-onna who considers herself Nube's true partner.

In the alternate timeline of "Reibaishi Izuna: Ascension," Ritsuko becomes Nube's caretaker during his hospitalization for an unspecified condition. For practical reasons related to his care, she cuts her long black hair short, remaining unaware of the true nature of his ailment. She has purple eyes and typically wears professional attire, including a yellow jacket and dress. Her surname "Takahashi" means "tall bridge," and her given name "Ritsuko" combines "ritsu" (commandment) and "ko" (child).