Tōko Yotsuya is the widow of Mamoru Yotsuya and mother to Miko and Kyōsuke Yotsuya, her husband having passed before the series begins. She possesses chest-length jet black hair typically secured in a low side ponytail resting on her right shoulder by a light blue scrunchie. Her bangs sweep left with chest-length strands framing both sides of her face, complemented by striking golden eyes. Her appearance retains a notably youthful quality, contrasting with her role as mother to a high school-aged daughter and elementary school-aged son. Miko Yotsuya shares these distinct physical traits, closely resembling her mother.

Tōko met and built a life with Mamoru, raising their two children. She and Kyōsuke form a protective family unit, both expressing concern for Miko's well-being while remaining unaware of Miko's ability to perceive spirits. Her surname "Yotsuya" translates to "four valleys," and her given name "Tōko" combines the kanji for "transparent/permeate" and "child."