As a child, Uta—the Red Hair Pirates' ex-musician and Monkey D. Luffy's childhood friend—promised that she would build a new era of freedom by performing joyful music for the world. Luffy and the Straw Hat Crew arrive at Uta's first ever live concert, where many fans have gathered to enjoy the diva's otherworldly singing. Due to a childhood trauma, Uta bears a deep-seated hatred for pirates; her happy reunion with Luffy is cut short when she learns that he has since become one. Luffy's refusal to change his ways results in Uta unleashing her powers on the Straw Hats. The crew soon learns that their minds have already been trapped in Uta's dream world since the beginning of the concert, while their unconscious bodies remain asleep in the real world. With time quickly running out, the Straw Hats must find a way to escape the nightmare or be trapped in Uta's dream forever.

The legendary former hitman Tarou Sakamoto has thwarted numerous assassins after an enormous bounty on his head was issued. But he cannot seem to catch a break and simply take it easy with his beloved family. A mysterious and infamous figure known as Slur has brought a group of insane death row inmates to Japan, who hold back from nothing to eliminate their targets. Sakamoto is not the only target—the criminals have been assigned to kill various other people, including the new hires at Sakamoto's convenience store, Shin Asakura and Lu Shaotang. The situation escalates even further when the Order, a group of the most skilled Japanese assassins, becomes involved. As the inmates begin wreaking havoc, Sakamoto and his allies must remain vigilant for the sake of everything they hold dear.

The Four Cardinal Heroes are a group of ordinary men from modern-day Japan summoned to the kingdom of Melromarc to become its saviors. Melromarc is a country plagued by the Waves of Catastrophe that have repeatedly ravaged the land and brought disaster to its citizens for centuries. The four heroes are respectively bestowed a sword, spear, bow, and shield to vanquish these Waves. Naofumi Iwatani, an otaku, becomes cursed with the fate of being the "Shield Hero." Armed with only a measly shield, Naofumi is belittled and ridiculed by his fellow heroes and the kingdom's people due to his weak offensive capabilities and lackluster personality. When the heroes are provided with resources and comrades to train with, Naofumi sets out with the only person willing to train alongside him, Malty Melromarc. He is soon betrayed by her, however, and becomes falsely accused of taking advantage of her. Naofumi then becomes heavily discriminated against and hated by the people of Melromarc for something he didn't do. With a raging storm of hurt and mistrust in his heart, Naofumi begins his journey of strengthening himself and his reputation. Further along however, the difficulty of being on his own sets in, so Naofumi buys a demi-human slave on the verge of death named Raphtalia to accompany him on his travels. As the Waves approach the kingdom, Naofumi and Raphtalia must fight for the survival of the kingdom and protect the people of Melromarc from their ill-fated future.