Asahi, the protagonist, is suddenly transported to another world in an unforeseen accident. His older sister, Maya, is infatuated with him and chases him into this strange land. Thus begins a tale of adventure as the two embark on a chaotic life in this strange land where they encounter new friends. In essence, as the story progresses, the characters gain new allies and quests in a rhythm that is familiar to fans of the isekai genre. Meanwhile, this is also a story of the growth of the protagonist, Asahi. Although his older sister has abilities so powerful that they’re practically cheating, he is on the opposite end of the spectrum with low stats. Yet he does not resign himself to this fate and struggles hard throughout the series to succeed. The anime adaptation will focus on the story told in the first five volumes of the manga, in which Asahi and Maya are transported to this new world, battle their rival Kirumaria, they meet new friends, they save a town from a deluge of a slimes, and Asahi assembles his party of companions.
High school student Asahi Ikusaba gets lost in another world and immediately falls into a crisis. Soon after, Mayu Ikusaba, his big sister with a brother complex, suddenly appears, having followed him to the other world.