Hijiri is a model with a significant amount of clout for the lax life she and her friends live. Being the most maturely characterized from the outset, she is also the first person in Kana's life to present one of many quandaries the protagonist will have with maturity.
Since her first mention, Hijiri was given a level of clout that the other characters greatly admire. She has multiple modelling shoots under her belt that resulted in appearing on a magazine cover, addresses it with coy sarcasm about paparazzi, and turned her romantic attention towards older guys. During this time, she's noticeably absent from her friends' meetups and Kana even takes notice of her nails, painted glitter when they last hung out, being covered with a more sophisticated pink. Originally built up as the pinnacle of maturity and adulthood, Hijiri makes a gradual shift throughout the series to a more normal teen life, starting in episode 2. She seemingly stops modelling and takes up a waitress job at a karaoke restaurant, admits her previous "mature" behavior was a facade, and enjoys her "immature" side with the rest of her friends. She has a surprising amount of empathy for the relationship that started this, protecting Toshio from Mossan's attack and Pets and Kana's words because she sees them as the same at the time. Deep down, she may not have known she was being inauthentic, but seeing it in Toshio's careless indecisiveness opened her eyes. She grew to be more of her own person as a result, strengthening her friendships with those around her.
Hijiri has long, voluminous black hair with wispy bangs and striking blue eyes. Her lips are plump and usually colored pink for special events or a shade darker than her skin tone for casual times. She is shown to have manicured pink nails in more detailed shots. She has a soft jawline, sharp chin, and thin black eyebrows. Outside of school, she wears a variety of stylish outfits that compliment her body. For school, she wears the uniform of a cream jacket over a collared white shirt, short red tie, and dark blue skirt. She adds knee-high black socks and white slip-ons with red soles to it, as well as carrying her backpack on just one shoulder.
Hijiri and Kana appear to have a solid friendship. Kana really looks up to Hijiri, mainly because Hijiri appeared to be the most mature of their group of friends. She dates older men, dresses stylishly, looks much older than she is, and doesn't take things like relationships seriously. However, Hijiri was merely pretending to be mature. Kana wants nothing more than Hijiri to be happy, but also wanted Hijiri and her boyfriend to remain together, as Kana has an infatuation with maturity due to her own immaturity. She attempts to "fix" Hijiri's relationship behind her back by setting up a meeting with them both at the same place. The resulting confrontation is the first to teach Kana that sometimes her actions are unwelcome. Hijiri turns her disconcert with Kana's actions on Toshio when he tries to side with her on maturity, however. In many ways, Kana at that time is the opposite of Toshio, who reflects Hijiri's false persona more and thus becomes a thing she dislikes. This subsequently expresses to Kana that Hijiri learned from her breakup that she should enjoy being her own age instead of trying to act older, something that resonates with Kana's view and shows her priority of their friendship. They remain close through thick and thin for the rest of the series.