Takehiko Kuki studies at Kichijouji Seijou Gakuen and works on the school newspaper with Kojiro Souma, Yousuke Miura, and Saki Yagami. Secretly, he serves as a Shinyuu ninja, combating supernatural threats alongside Marika Kusaka and an unnamed priest. Takehiko possesses innate magnetite perception, enabling him to detect and battle demons.

Trained as an exorcist, he fights using twin knives and martial arts. He shows distinct reluctance when confronting humans possessed by demons, revealing a moral conflict within his duties. During an attack orchestrated by Akito Kobayashi, where kobold-possessed classmates target Saki Yagami, Takehiko intervenes with Marika, repelling the threat and safeguarding Saki.

His actions primarily unfold during nighttime confrontations across Tokyo's urban landscape. He arrives too late to join the final clash between the reawakened Masakado and the demon Ose, limiting his direct role in that battle's conclusion. His character development and background remain confined to his documented role as a supporting protector across official media.