A young girl with short red hair, usually wearing a flower pin with a buttoned sweater and skirt.
Okuyama is very mature for her age. In contrast with Souta's carefree and trusting nature, she is much more cynical and cautious. She often scolds Souta and their classmates for their childish behavior, but mostly because she is self-conscious of her forehead, which she thinks is too large. However this feeling about herself changed after Miyamura told her that she looked pretty.
Okuyama and Souta are friends and classmates. When asked by Iura if they are "just friends", she "obviously", noting that it's still 10 years too early for Souta to understand. Okuyama often goes over to the Hori house after school to play with Souta.
In much the same way Souta looks up to Miyamura as his "older brother", Okuyama looks up to Tanihara in a similar fashion. Despite Tanihara's relative reticence, and not being very good with children, Okuyama still clings to him and enjoys talking to him. However, Okuyama will sometimes view their relationship as them being equals, sometimes talking as if she's older than Tanihara.
Okuyama looks up to Hori as an older sister. She thinks of her as kind, cute and good at cooking. In addition, the two share a similar aesthetic when it comes to Hori's handmade stuffed animals.