Arata Kishimo is the central male protagonist, a seventeen-year-old second-year high school student. His surname combines the Japanese characters for "demon/ogre," "officer/boss," and "like/likeness," while his given name means "fresh, new." After his father's death, he lives apart from his mother. His family lineage grants him supernatural astral projection powers, enabling his spirit to leave his physical body. This ability becomes crucial when he searches for his childhood friend, Mio Miyamasu, following her accident.

Their close bond faces tension when Mio develops unexpressed romantic feelings. During a visit to his aunt Orika's fortune-teller booth, Arata perceives mysterious white orbs. His protective reaction—pulling Mio away abruptly—sparks an argument, straining their relationship. After Mio falls comatose from a traffic accident and her spirit enters the World Border, Arata visits her hospitalized body. He receives a mysterious phone call from Mio within that realm, prompting him to seek guidance from Orika. Using his astral projection, he enters the World Border to assist Mio, her fish's personification Kiku-chan, and the alien plushie Gimon. They confront Mogari, the guardian obstructing Mio's return.

Ultimately, Arata brings Mio's physical body to a cliff tied to their shared memories. His presence and actions there help Mio reclaim her "desire" to return to the human realm and reunite with him.