Haruaki Yachi is a high school boy and naturally resistant to curses. His father, Honatsu, sends him cursed instruments called "Worse" to try to break this. One day, Haruaki receives a black cube from Honatsu. During the night, he encounters a naked silver-haired girl stealing rice crackers. She is the human form of the black cube, an instrument of torture called "Fear in Cube". Haruaki and the girl "Fear" fight together against other Worse instruments and their owners using Fear's 32 mechanisms of torture.
Set in the year 2039, Japan is the under the rule of a multinational military force called GHQ after the country went into chaos due to the "Lost Christmas" incident ten years prior to the start of the series, when a giant outbreak of an alien virus called the Apocalypse Virus spreads during Christmas, causing the United Nations to send the GHQ to contain the outbreak and restore order. The series follows Shu Ouma, an intelligent yet socially awkward teenager who finds himself caught in the war between the GHQ and "Funeral Parlor (Undertakers)", a resistance organization led by Gai Tsutsugami, which aims to liberate Japan from the GHQ, when he meets Inori Yuzuriha, the famous Internet Singer of the band Egoist and a member of the Undertakers. Due to various circumstances, Shu acquires a genetic weapon called the Void Genome, also known as "power of kings", which allows him to extract "Voids", objects with special properties that reflect the personality of their owners from underage individuals. With his new powers, Shu joins the Undertakers to protect Inori and learns secrets and mysteries he never knew.
Set in the Shinigami technical school for weapon meisters, the series revolves around 3 groups of each a weapon meister and a human weapon. Trying to make the latter a "Death Scythe" and thus fit for use by the Shinigami, they must collect the souls of 99 evil humans and 1 witch.