In a realm where individuals called Killer Demons excel in distinct lethal techniques, two tales unfold, each focusing on a character's fateful brush with one of these formidable beings. Killer Queen and Deep End, initially not victorious in a Dengeki competition, predated the release of Toaru Majutsu no Index. Its emergence in 2004 was a response to Index's soaring fame. In a similar vein, Killer Device and Never End emerged in 2005, spurred by the acclaim garnered by the initial narrative.