Yō Kasukabe hails from an unspecified future era in her home world. Before arriving in Little Garden, she endured hospitalization for an unnamed condition that left her unable to walk. Her father gifted her a wooden pendant called the "Genome Tree - Non Priorum" or "Gnome Tree," the source of her supernatural abilities. This pendant facilitated her first meaningful connection, with a calico cat whose traits restored her mobility. Consequently, she formed deep bonds with animals but lacked human friendships prior to her summoning.

Physically petite with short brown hair usually secured by a side hair clip, Yō wears an ankle-length blue and white jacket split below the thighs, a white blouse, brown shorts, black knee-high socks, and tall brown boots. She always wears her father's pendant.

Her personality blends quiet introspection with underlying confidence. Preferring animal company to human interaction, she exhibits significant social reservation yet approaches danger or the unfamiliar with curiosity and resolve. Her friendship with Asuka Kudō marks her first meaningful human connection, which she treasures. A recurring trait is her reluctance to accept help during Gift Games, stemming from a desire not to burden others. This tendency creates critical vulnerabilities in confrontations, like refusing partner support against opponents Ayesha and Jack.

Upon arriving in Little Garden, Yō immediately demonstrated her capabilities in an introductory Gift Game. Her early challenges included volunteering for a high-stakes duel against Shiroyasha's griffin, wagering her life to stay mounted despite subzero temperatures. Successfully befriending the griffin granted her permanent flight. During the Galdo Gasper conflict, she sustained injuries protecting Asuka and community leader Jin Russel. Her character development culminated when Ayesha and Jack exploited her self-reliance as a weakness in their Gift Game. This defeat prompted her realization that accepting comrades' aid does not mean burdening them.

Yō's abilities center on animal communication and trait assimilation. She converses with species like birds, penguins, dolphins, and her calico cat, though effectiveness varies. By forging genuine animal friendships, she permanently acquires their physical attributes without coercion. Documented assimilations include walking prowess from her calico cat, flight from the griffin, and unspecified capabilities from other creatures. The pendant enables these abilities but never forcibly extracts traits.

In the OVA "Hot Springs Tour Chronicles," Yō appears without substantial narrative development beyond her established traits. She has no documented presence in spin-off media or sequel light novel series.