Two men have just arrived at a location known as Quindecim and are unable to remember how they got there. They are immediately greeted by a young woman who escorts them to a small bar, where a bartender awaits them. They are told that they will have to participate in a game, randomly chosen by roulette, and will be unable to leave until its completion; if they refuse, the consequences will be dire. In addition to the rules of the game, the two men are told to play as if their lives are at stake. The game that has been chosen is billiards. But there's more to it than just pocketing pool balls, as the two are about to find out the outcome could mean life or death.

Due to a careless mistake, god of wind Silphyleel unintentionally kills a 28-year-old man named Takumi Kayano. Unfortunately, Silphyleel cannot return Takumi to Earth. Instead, the deity reincarnates Takumi into the fantasy world of Etelldia. Equipped with an assortment of magical powers and bottomless inventory, Takumi spawns in the Forest of Gaia, where high-level monsters roam free. There, he meets five-year-old twins who, despite the dangerous environment, are still alive thanks in part to their extraordinary physical strength. Takumi decides to take them under his wing, naming them Allen and Elena. As the trio embarks on their grand adventure in Etelldia, their very existence may impact the world's destiny.

Childhood friends Tomo Aizawa and Junichirou "Jun" Kubota do everything together, whether it be training or just enjoying a fun day out. Anyone would think that these two are best friends for life. The only issue is that the tomboyish Tomo is in love with Jun, but he regards her like a brother. At the start of their first year of high school, Tomo confesses her feelings to Jun. However, her rough mannerisms and lack of hesitance to throw a punch do nothing to sway Jun's heart. Realizing that he will remain indifferent to her affections unless she does something about it, Tomo must find a way to knock some sense into Jun and open his eyes to what is right in front of him.

Frustrating, insufficient, and irritating is how most citizens would describe civil servants. However, three new employees are about to discover what really happens behind the scenes. Lucy Yamagami, bent on revenge against the civil servant who allowed her comically long name to be put on her birth certificate; Yutaka Hasebe, an easygoing guy always on the lookout for a place to slack off; and Saya Miyoshi, a nervous first-time worker, are about to experience the underwhelming satisfaction of being government employees. They are supposed to be trained by Taishi Ichimiya, but he has no idea how to do so, even though he has worked there for eight years. With an incompetent senior colleague and unfavorable confrontations with clients, the trio starts to lose faith in their chosen occupation but encourage each other to do their best.