Haruka emerges in the series' third episode, "Natsu Matsuri" (Summer Festival), as Yukari's close friend. Their narrative unfolds during a Lantern Festival, a tradition permitting spirits of the departed to briefly revisit the living world. Yukari attends hoping to reunite with Haruka, revealing Haruka's prior passing. The story centers on themes of loss and their poignant reunion, emphasizing Yukari's emotional journey and the bittersweet impact of Haruka's spiritual presence during this fleeting encounter.

Introspective and creative, Haruka harbors a deep passion for writing. She frequently isolates herself in her small apartment, absorbed in stories and thoughts, fostering loneliness and isolation. Significant self-doubt and insecurity about her writing abilities plague her, preventing her from sharing work and fueling a cycle of hesitation in creative pursuits.

Her development stems from friendship with Elena, an aspiring writer whose outgoing nature contrasts Haruka's reserve. Through Elena's influence, Haruka gradually embraces creative risks and openness. She comes to view writing as both personal expression and connection with others, shifting her perspective toward greater confidence and optimism about her future as a writer.