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.

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.

The happy-go-lucky Michi Sonoda announces to her teammate, Sanae Takigawa, that she will quit judo for good after her final middle school tournament. This leaves Sanae in disbelief; after all, it was Michi's passion toward the sport that reeled Sanae into judo in the first place. Michi claims that a well-spent youth should be associated with things such as getting a boyfriend rather than sweaty tatami mats. However, Michi's plan to end her fledgling judo career with a bang is spoiled after experiencing an embarrassing defeat at the hands of the talented Towa Hiura. Later, her plan is further derailed when she finds out that Towa has enrolled in the same high school as herself and Sanae. With the sudden appearance of her past foe, Michi may soon realize that she still has lingering feelings for the sport of judo.

Tricked into assassinating his own prospective father-in-law, righteous samurai Raizou Kurima is overwhelmed with guilt. In order to reclaim his honor, Raizou swears vengeance on the lord who gave him those misleading orders. In his pursuit, he is aided by self-proclaimed merchant-of-all-trades Yuuen Usui, who is actually one of the Revengers—assassins who seek justice for the wronged and dispense bloody revenge on their behalf. Tragedy seems destined to follow Raizou as he becomes increasingly intertwined with members of the Revengers. As he begins working as a vigilante alongside them, the complicated web between the corrupt Japanese political elite, the unscrupulous Europeans, and the Revengers gradually reveals itself. The more entangled he becomes in these affairs, the more Raizou realizes that justice is as deceptive as the honor that he sought to redeem.