Wakaba Himeji, a fifth-grade elementary school student, possesses the distressing ability to see malevolent spirits invisible to others. This power leads to social isolation as the spirits harm those near her. Bullied by classmates who call her a "liar" or "witch," she has no friends and appears withdrawn, rarely smiling, with a demure and taciturn personality. Physically, she has long black hair, black eyes, and typically wears a plain yellow dress with black underclothing.

Her life changes upon discovering a small pink creature named Pupipo (or Pō-chan) in a street box. Pupipo can perceive and fight the malicious spirits plaguing her, offering protection. This encounter helps Wakaba open up socially. She befriends Reiko Azuma, a transfer student fascinated by the occult and her first genuine friend, and meets Naoya Yūki, a classmate who also sees spirits (including their pasts upon touch). With Pupipo's aid and these relationships, she confronts challenges like bullying from peers Miyori Sonoda and Ryōhei Ameyama.

A pivotal event occurs when Reiko Azuma suffers a near-fatal accident. Wakaba and Pupipo journey into the afterlife to rescue Reiko from crossing over, confronting a spirit holding a grudge linked to Reiko's death. Pupipo's origin is later revealed as intrinsically tied to Wakaba's future: in an alternate timeline, Wakaba miscarried due to demonic interference, and her unborn child's primordial spirit became Pupipo. This entity violated reality to travel back in time, ensuring Wakaba's liberation from her spiritual burdens so he could eventually be born, creating a stable time loop. This culminates in Wakaba being freed from her ability to see spirits, allowing a normal life.

Initially wary of her bringing home strays due to past troubles caused by her powers, her parents accept Pupipo out of concern for her loneliness. Her father exhibits protective instincts, ready to defend her even against those he initially sought for help.