Hijiri Yajima is one of the primary supporting characters in FLCL: Shoegaze and a close friend of the protagonist, Kana Koumoto. She is a high school student who also works as a model, a role that has given her a significant amount of social clout among her peers. Initially, Hijiri is characterized by a sophisticated and mature demeanor that sets her apart from her friends. She is seen dating older men, wearing stylish and adult-oriented clothing, and speaking with a coy, experienced sarcasm about her life in the public eye, having appeared on a magazine cover.

Throughout the series, this outward persona is revealed to be a carefully constructed facade. Hijiri experiences a gradual but significant shift away from her performative maturity, beginning as early as the second episode. She stops modeling and takes a job as a waitress at a karaoke restaurant. In a moment of self-realization, she admits that her previous behavior was inauthentic and begins to embrace a more normal teenage life, enjoying her "immature" side with her friends. This internal conflict and eventual change form the core of her character arc. Her primary motivation stems from a desire to appear grown-up, but her journey leads her to understand the value of being true to her actual age and self. She learns to prioritize genuine friendships over a hollow performance of adulthood.

Hijiri's most significant relationship is with Kana. Kana initially looks up to Hijiri as the pinnacle of maturity, wanting nothing more than for her to be happy. However, this admiration leads Kana to interfere in Hijiri's romantic relationship behind her back, an act that Hijiri finds unwelcome and which becomes a crucial learning experience for Kana about respecting boundaries. Hijiri also has a boyfriend named Toshio, and it is through her breakup with him that she gains clarity. She sees her own false persona reflected in his careless indecisiveness, which opens her eyes to her own inauthenticity. Despite the temporary friction caused by Kana's meddling, their friendship remains strong, and Hijiri's growth ultimately reinforces the bond between the group.

In terms of development, Hijiri transforms from an aspirational but fake figure of adulthood into a more grounded, self-aware individual who is comfortable with being a teenager. Her notable abilities are not supernatural but social and emotional. She possesses a surprising amount of empathy, which she displays by protecting Toshio from the attacks of another friend because she recognizes a part of herself in him. Furthermore, her initial power comes from her status and clout as a model, which she ultimately abandons to pursue a more authentic life. In a glimpse of her future shown when she is twenty years old, her hair is cut shorter, and she is seen in a casual setting with a dog, illustrating the comfortable, stable life she has found after leaving her performing days behind.