Kyoko Yoshizawa, Hiroshi's girlfriend, comes from a relatively wealthy family. Despite this privileged background, she wields a strong-minded independence, readily standing up for herself and joining Hiroshi in playful pranks, tempered by a kind-hearted nature. She initially feigned dislike towards Hiroshi, secretly nurturing romantic feelings since their first meeting, and desired a formal proposal on their initial date, revealing traditional romantic expectations. Her perception of Hiroshi shifted upon seeing the Pyonkichi frog imprint on his shirt; mistaking it for a decorative design she found endearing, it paved the way for a closer friendship.

Academically, Kyoko excels, achieving higher grades than Hiroshi. Her hobbies include ice skating. In her relationship, she reacts cautiously to Hiroshi's public advances, particularly avoiding overt affection in social settings. Yet, she exhibits possessiveness and intense jealousy when Hiroshi interacts with other girls, notably Kuniko Obayashi, his flirtatious childhood sweetheart. Despite these tensions, Kyoko and Hiroshi developed a mutual understanding, spending significant time together and maintaining a stable bond. Her character arc includes a future depiction where she marries Hiroshi, as shown in the Solmac advertisement series created by the original animators.