In a war against four overpowered races—angels, demons, undeads, and humanoid beasts—humanity could only prevail thanks to its champion Sid, who defeated the other races' champions and sealed away their armies in four pyramids. In an age where Sid's existence has become but a legend of the past, Kai Sakura Vento is one of the many conscripts tasked with monitoring the pyramids in fear that these old foes would escape. On a peaceful day while spending time with his friend Jeanne E. Anise, the world is suddenly overwritten, transporting Kai to an alternate reality where humanity has nearly been annihilated by the demons and forced into hiding. To make matters worse, his very existence has been erased from this world; all of his friends, including Jeanne, who leads the local resistance efforts in this world, have forgotten about him. Trying to investigate the remains of his former world, Kai encounters Rinne, an enigmatic young woman trapped in a pyramid. Mysteriously inheriting Sid's legendary sword Codeholder, Kai manages to free Rinne from her imprisonment. Determined to fix this reality, Kai joins forces with Rinne and Jeanne to free humanity from demonic rule. But if the valiant soldier wants to have a chance at returning to his original world, he will first have to uncover the cause behind the mysterious alteration of reality.

Nikola is just a village girl working at the inn...until the day dragons invade, and she meets Haga, a scholar of everything around him. He's a part of an elite society called Seeker, created to address a series of maladies plaguing their usually peaceful world. But both Nikola and Haga have secrets they hide...ones that will change each other's very existence... (Source: Kodansha USA)

Rimuru Tempest is victorious following his climactic showdown with Demon Lord Clayman. With Diablo's aid, the war with the Falmuth Kingdom ends decisively in Rimuru's favor. Fueled by increased migration and the integration of Jura Forest, the nation of Tempest undergoes rapid growth. Rimuru's victory shifts the balance of power, giving rise to a renewed period of peace—but whether that peace will last is another matter. Yuuki Kagurazaka and Kazalim are conspiring with the Harlequin Alliance to bring about Rimuru's downfall. Furthermore, the Western Holy Church continues its intolerant crusade against Rimuru and his non-human subordinates. Both allies and enemies engage in a battle of wits, carefully advancing their agendas without shattering the delicate status quo. But once the first domino inevitably falls, the race to supremacy begins.

Duke Fleed is a survivor of the Fleed Planet who has escaped to Earth. Onboard a mysterious spaceship, he is raised by Dr. Umon as his adoptive son, and becomes known as Daisuke Umon. Years after his arrival, he's faced with the threat of King Vega and his army, who want to conquer the Earth. With his friends Koji and Hikaru and later his younger sister Maria Grace, Duke decides to fight back using his best weapon - the almighty Grendizer.