Now that Koyomi Araragi and Hitagi Senjougahara have graduated, very few familiar faces remain at Naoetsu Private High School. One of these is Suruga Kanbaru, holder of the Monkey's Paw. When she begins to hear talk of a mysterious being known as the Devil who will magically solve any problem, Kanbaru immediately thinks these rumors are about her and decides to investigate. She discovers the Devil is actually Rouka Numachi, a former basketball rival from junior high who is no longer able to play due to a leg injury. Rouka provides free advice to those who seek her out. Acting as a collector of misfortune, she enjoys relieving the stress of her clients by providing them with the false hope of having their problems solved. Although Kanbaru sees no real harm being done, she reprimands Rouka for lying and heads home, relieved she is not the cause of the rumors. But she may have a reason to worry after all: she finds that her left hand has reverted back to its human form.

The day is as normal as it can be in high school as the students peacefully go about their everyday activities until an unprecedented catastrophe strikes the school, killing every person in its wake. Guided by what seems to be a miracle, a handful of students are fortunate enough to be reincarnated into another world as nobles, princes, and other kinds of people with prestigious backgrounds. One girl, however, is not so lucky. Being reborn as a spider of the weakest kind, she immediately experiences the hardships of her dire situation. Even so, she must press on to survive the numerous threats that endanger her life. Discovering that her new world has a system like that of an RPG, she tries her best to hunt prey and defeat monsters to level up and evolve. As she gradually grows stronger, she hopes one day her efforts will be rewarded, and that she will be granted a better life.

Fifteen years ago, disaster struck human civilization, and now dangerous man-eating monsters roam the ravaged lands, posing an existential threat to the remaining survivors. Amid this turmoil, an isolated facility shelters children and nurtures them in peace. However, as a few among them find out about the world beyond the narrow periphery of their nursery's walls, their curiosity about it slowly grows. Meanwhile, in the outside world, young survivors Maru and Kiruko band together to search for a special place called Heaven, each for their own reasons. Carrying past burdens and tragic secrets, the two hope to find answers to the cruelty they have experienced in their lives and in the world, which still remains in tatters.

Yuu Izumi leads a high school life filled with one mishap after another. No matter how improbable the situation, unfortunate events strike him at every turn. In possession of such terrible luck, Izumi enters his second year with a single wish in mind—to spend more time with his affectionate girlfriend, Micchon Shikimori. Cute, athletic, and caring, Shikimori is immensely popular at their school. But since they began dating a year ago, Izumi has witnessed a surprising side to his otherwise adorable girlfriend: when the need arises, she turns incredibly cool! His misfortunes are easily avoided when she is there to protect him with an awe-inspiring look on her face. Charming in every way, she never ceases to make his heart skip a beat. Unfortunate as he may be, Izumi is sure to see his days of bad luck end thanks to the cute yet cool Shikimori.