Mirai Kuriyama is the sole survivor of a clan of Spirit World warriors with the power to employ their blood as weapons. As such, Mirai is tasked with hunting down and killing "youmu"—creatures said to be the manifestation of negative human emotions. One day, while deep in thought on the school roof, Mirai comes across Akihito Kanbara, a rare half-breed of youmu in human form. In a panicked state, she plunges her blood saber into him only to realize that he's an immortal being. From then on, the two form an impromptu friendship that revolves around Mirai constantly trying to kill Akihito, in an effort to boost her own wavering confidence as a Spirit World warrior. Eventually, Akihito also manages to convince her to join the Literary Club, which houses two other powerful Spirit World warriors, Hiroomi and Mitsuki Nase. As the group's bond strengthens, however, so does the tenacity of the youmu around them. Their misadventures will soon turn into a fight for survival as the inevitable release of the most powerful youmu, Beyond the Boundary, approaches. [Written by MAL Rewrite]

Kind-hearted Himuro-kun is unfortunate: when in deep concentration, stressed, or flustered, he involuntarily creates blizzard conditions for himself and anyone in his vicinity. During one such incident on the first day of his new job, Himuro-kun encounters the beautiful Fuyutsuki-san, who helps him break out of his nerve-induced ice. As it turns out, Fuyutsuki-san is his new coworker. At the office, the cool-headed Fuyutsuki-san offers simple and rational solutions to Himuro-kun's icy dilemmas—everything from helping him garden without freezing his plants to ensuring he does not melt during their tropical work retreat. Every time Fuyutsuki-san does something kind for him, the tempest of emotions he experiences inside embarrassingly manifests on the outside. As a result of the frequent snowstorms, Himuro-kun's feelings for Fuyutsuki-san are impossible to hide. Even though Fuyutsuki-san is unfamiliar with love, Himuro-kun remains determined to repay her kindness and warm her heart in any way he can.

The number of terrorist acts in Japan has never been lower, thanks to the efforts of a syndicate called Direct Attack (DA). The organization raises orphaned girls as killers to carry out assassinations under their "Lycoris" program. Takina Inoue is an exceptional Lycoris with a strong sense of purpose and a penchant for perfection. Unfortunately, a hostage situation tests her patience, and the resulting act of insubordination leads to her transfer out of DA. Not thrilled about losing the only place she belonged to, she reluctantly arrives at her new base of operations—LycoReco, a cafe in disguise. Takina's new partner, however, turns out to be quite different from what she imagined. Despite being the famed Lycoris prodigy, Chisato Nishikigi appears almost unconcerned with her duties. She drags Takina along on all kinds of odd jobs under the simple explanation of helping people in need. Takina is even more puzzled when Chisato takes down a group of armed assailants without killing any of them. Feeling like a fish out of water, Takina itches to get reinstated into DA—but Chisato is determined to prove to her that there is more to a life than just taking them.

High above the realm of man, the gods of the world have convened to decide on a single matter: the continued existence of mankind. Under the head of Zeus, the deities of Ancient Greece, Norse mythology, and Hinduism, among others, call assembly every one thousand years to decide the fate of humanity. Because of their unrelenting abuse toward each other and the planet, this time the gods vote unanimously in favor of ending the human race. But before the mandate passes, Brunhild, one of the 13 demigod Valkyries, puts forth an alternate proposal: rather than anticlimactically annihilating mankind, why not give them a fighting chance and enact Ragnarök, a one-on-one showdown between man and god? Spurred on by the audacity of the challenge, the divine council quickly accepts, fully confident that this contest will display the utter might of the gods. To stand a chance against the mighty heavens, Brunhild will need to assemble history's greatest individuals, otherwise the death knell will surely be sounded for mankind.