Tooru Oshikiri is a high school student defined by a dour personality and short temper, who fixates on his height. His wealthy family provides a large, remote house where he lives alone while his parents work overseas. This isolation plunges him into strange and terrifying manifestations, possibly hallucinations or supernatural phenomena. When facing these events, like discovering a petrified body within his home's wall, he experiences fear but deliberately suppresses his emotions to cope.

These disturbances involve an alternate version of himself from another dimension. This double invades his reality, commits murders, and conducts experiments using a height-altering chemical formula on people, resulting in horrific mutations. The alternate disposes of the mutated victims by discarding them into Oshikiri's dimension. He claims to be the "real" Tooru Oshikiri, branding the original an impostor. Multiple Oshikiri versions exist across dimensions, though only one alternate appears directly.

Throughout these ordeals, Oshikiri interacts with secondary characters, including classmates and acquaintances such as Nakajima, Takayuki, Hotta, Kojima, Kozue, Yumiko, Satomi, Kamiyama, Watanabe, Koizumi, and Mio Fuji. His parents are mentioned but remain absent.

His name "Toru" (トオル) carries potential kanji interpretations: 徹 ("pierce, penetrate") or 亨 ("pass through, go smoothly"). His surname "Oshikiri" translates to "short mane".