In canonChiyo and Osaka have a friendly relationship, as the former is Osaka's closest friend from her class. It begins when Osaka joins Chiyo's class and they team up for a P.E. lesson. One of the main ways in which they are similar is that they are both terrible at physical education, as seen when they ran the marathon and both ended up gasping for breath afterwards. They both have kind personalities and are calm in temper. Chiyo is the one who is most intrigued by Osaka's strange theories and thinking and seems to understand them best. This is likely due to Chiyo's childlike naivety which Osaka shares. This aspect of their relationship is perhaps especially clear in the manga. Chiyo also respects Osaka enough to use the formal suffix "-san" when referring to her (as in "Osaka-san"), something she does with everyone except Tomo.
During the part seen entirely through Chiyo-chan's eyes, she reflects on how often Osaka falls asleep in class and speculates that Osaka might be a night owl. She also appreciated Osaka's efforts in cleaning, albeit she was not very good at it.Right from the beginning of their time spent together, Osaka has been fascinated with Chiyo's pigtails, almost to the point of obsession. She dreams about them several times, daily and nightly. Most of Osaka's dreams in general involve Chiyo in one way or another. In her dreams, Chiyo's pigtails allow her to fly, are detachable, and/or control her. This sometimes scares Osaka so much that she has to test it in real life so as to be sure that it was all a dream. When Chiyo changed her hairstyle, Osaka initially believed that her pigtails had moved on their own.