Yukari Tenkawa is Takagi and Nishikata's classmate, forming a close trio with friends Mina Hibino and Sanae Tsukimoto. She sports long brown hair in a high ponytail, glasses, and has a center parting secured by four hairpins. Her sharp eyes sometimes unintentionally intimidate children. She is the tallest among her friends in school, though Sanae later surpasses her.

As class representative, Yukari exhibits a studious nature, consistently completing homework and studying diligently for tests, yet remains an academically average student. She displays a quiet demeanor but often acts as the responsible figure within her friend group, reprimanding Mina and Sanae for slacking on studies or childish behavior. She experiences frustration when her friends prioritize snacks over her preferred topics. Yukari harbors a strong interest in romance and mature discussions, frequently observing Takagi and Nishikata's interactions and expressing a desire for her own romantic relationship. Her friends' lack of shared enthusiasm during school days sometimes leaves her feeling isolated.

Her family includes a younger sister, Sae, and parents with a happy marriage. Yukari has picky eating habits, often trading lunch items with friends, and is sensitive to cold weather. She prefers indoor activities like reading manga, watching television, and eating sweets. Yukari lacks athletic ability and cannot swim, requiring flotation devices in water.

Her fascination with romance becomes the central focus in the spin-off "Koi ni Koisuru Yukari-chan," exploring her attempts to initiate romantic conversations, though she often talks alone due to her friends' disinterest.

As an adult in "Karakai Jōzu no (Moto) Takagi-san," Yukari works as an office lady. She eventually becomes engaged, fulfilling her wish for marriage, but experiences pre-wedding anxiety ("marriage blues"), leading her to seek comfort from Takagi. Mina and Sanae help calm her nerves. Takagi, Nishikata, and their daughter Chi attend her wedding, where she appears calm and happy. Her adult style involves formal attire like blazers and skirts or casual long skirts and tops, without hair clips.

Throughout school and into adulthood, Yukari maintains her friendships. She visits Mina at her kindergarten workplace and, with Sanae, occasionally tails Takagi's family to observe family dynamics, stemming from her curiosity about married life as she prepares for her own marriage.