When Hiyori⁠—a young girl whose deceased father taught her the joys of fishing⁠—headed out to sea for some alone time, she never thought that she would encounter another girl there. After a while, this girl⁠—named Koharu⁠—and her end up fishing and cooking together, and they get to know each other a bit in the meantime. During their brief time together Koharu finds out that the reason Hiyori went out to sea that day was because she's hesitant towards meeting her new step family that same evening. But what a coincidence! Koharu is also meeting her new family tonight! "No. It can't be a coincidence..." Follow these two 'sisters' and their new life together!

Draw your weapons and take aim, because Sabagebu! is coming at you! Momoka Sonokawa was just minding her own business on the train one day when she encountered a pervert. Before she could do anything about it, a girl named Miou appears, brandishing two pistols and and scaring him off, only to be arrested herself a few minutes later for possessing firearms. Later Momoka sees this same girl at her school and follows her to a run down building. It turns out Miou is the president of the school's Survival Game Club, and it doesn't take long for Miou to capture Momoka and force her into joining them. Over the course of the series, Momoka and her new “friends” will take part in multiple battles against enemies from other schools, a rival from the same school who wants to see the club shut down and even each other (on multiple occasions). With friends and classmates like these, will Momoka even make it to graduation?

Daisuke Higashida is a serious first-year student at Higashizaka High School. He lives a peaceful everyday life even though he is not satisfied with the family who doesn't laugh at all and makes him tired. However, his father's company goes bankrupt one day, and he can no longer afford allowances, cellphone bills, and commuter tickets. When his father orders him to take up a part-time job, Daisuke decides to work at a nearby family restaurant in order to avoid traveling 15 kilometers to school by bicycle.

Cool-headed and rational, Koujirou Shindou is a government official and master negotiator with a well-earned reputation. While departing on a business trip, a giant cube materializes and his plane is taken undamaged into the mysterious, indestructible structure. As Japanese authorities attempt to identify the cube's properties and origins, Shindou encounters an otherworldly entity known as Yaha-kui zaShunina, who materializes in the form of a human man. He assures Shindou that the passengers are not in any danger and requests help in negotiations with the human world. Hailing from a higher dimensional universe known as Novo, Yaha-kui zaShunina is able to transfer information between Novo and Shindou's universe through a cube called Kado. Despite having these unfathomable abilities, he does not appear hostile. Instead, he announces that he has come to this world with only one intention: to "advance" humanity—starting with Japan. [Written by MAL Rewrite]