Kanna Tajima is a supporting character in the story of River's Edge, known for being the naïve and vulnerable girlfriend of the male lead, Ichiro Yamada. She is an underclassman at the same high school as the main group of characters. Her role in the narrative is largely defined by her one-sided romantic relationship with Ichiro, which forms a key part of the story's exploration of misguided teenage desires and emotional isolation.

Kanna is characterized by her innocence and her desperate, self-deceptive optimism. She is deeply infatuated with Ichiro, whom she finds handsome and stylish, and she often boasts about their relationship to her schoolmates to elevate her own social standing. Unbeknownst to her, Ichiro is gay and is using the relationship as a social cover to hide his true sexuality from his peers. Despite his clear indifference and refusal to become physically intimate with her, Kanna resolutely turns a blind eye to the warning signs. Her primary motivation is to convince herself that she has found genuine love, clinging to the illusion of a perfect relationship to avoid facing the painful reality of rejection. This desperate attempt to fabricate happiness in a bleak and emotionally barren world ultimately leads to her own destruction, as her unrequited feelings and Ichiro's dishonesty cause her significant emotional pain.

In the wider story, Kanna serves as a contrast to the more detached and cynical characters like Haruna Wakakusa. While Haruna seems to have accepted the emptiness around her, Kanna actively fights against it by forcing a narrative of love and happiness, even when none exists. Her key relationship is, of course, with Ichiro Yamada. This relationship is entirely one-sided, with Kanna pouring her energy into it while Ichiro remains distant. A significant image associated with her is her persistent knitting of a sweater for Ichiro, a tangible symbol of the affection and future she imagines for them, which he does not truly want. Kanna does not possess any notable physical or extraordinary abilities; her defining characteristic is her relentless, albeit misguided, emotional determination. Her personal development is a tragic one, as she is an emotionally fragile girl who is ultimately left hurt and disillusioned by a relationship built on a lie. She is a quintessential representation of a teenager whose efforts to find meaning and love in a hostile environment only lead to her own despair.