Yayoi Fushimi, a ghost who died in World War II, was acquainted with Arashi and Kaja during her life. Her ethereal form weakened over time, requiring energy to sustain her existence. She resided in a dilapidated mansion with her best friend Kanako Yamazaki, their mutual dependence shaping their ghostly lives. Initially, Yayoi was half-paralyzed and wheelchair-bound due to a horrifying accident, a condition rooted in psychological trauma rather than physical injury.

Healing came when Hajime Yasaka facilitated a time-travel incident, allowing Yayoi to encounter Kanako again for the first time since their deaths. This event restored her mobility and resolved the trauma causing her paralysis. Her personality sharply contrasts with Kanako's, marked by pronounced naivety, absent-mindedness, and extreme shyness, particularly around men, alongside a quiet demeanor. She exhibited significant forgetfulness, struggling to recall simple things like dish or book names, leading to comedic misunderstandings. She often described items in overly poetic or indirect terms, resulting in errors like delivering a Rubik's Cube instead of food.

In the second season, her ability to form time-travel connections expanded beyond Hajime. She gained the capacity to link with Sayaka, the café owner, and Josephine, Takeshi Yamashiro's dog, enabling further time-travel adventures and shifting her social interactions with the living world. Her relationship with Kanako evolved from one-sided reliance to a more balanced friendship, influenced by their shared history and resolution of past conflicts like their initial attempts to drain Arashi's energy. During this period, Yayoi gradually overcame some of her shyness, participating more in group activities at the café and beyond.