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.

Thirty-seven-year-old Satoru Mikami is a typical corporate worker, who is perfectly content with his monotonous lifestyle in Tokyo, other than failing to nail down a girlfriend even once throughout his life. In the midst of a casual encounter with his colleague, he falls victim to a random assailant on the streets and is stabbed. However, while succumbing to his injuries, a peculiar voice echoes in his mind, and recites a bunch of commands which the dying man cannot make sense of. When Satoru regains consciousness, he discovers that he has reincarnated as a goop of slime in an unfamiliar realm. In doing so, he acquires newfound skills—notably, the power to devour anything and mimic its appearance and abilities. He then stumbles upon the sealed Catastrophe-level monster Storm Dragon Veldora who had been sealed away for the past 300 years for devastating a town to ashes. Sympathetic to his predicament, Satoru befriends him, promising to assist in destroying the seal. In return, Veldora bestows upon him the name Rimuru Tempest to grant him divine protection. Now, liberated from the mundanities of his past life, Rimuru embarks on a fresh journey with a distinct goal in mind. As he grows accustomed to his new physique, his gooey antics ripple throughout the world, gradually altering his fate.

A Magi is a magician whose inclination toward magic is so immense that they can be said to shape the world. With their significant influence, each Magi chooses a worthy candidate to become a king, then helps them conquer strange labyrinths called Dungeons and acquire the power of mythical djinns within. Above all else, the Magi supervises their elected representative as they build a country that might one day bring the world to its knees. Aladdin is a young Magi wandering the world in search of his true self. However, his journey is not a lonely one, as he is accompanied by his friend and mentor Ugo—a djinn he summons using his flute. In his travels, Aladdin also befriends Alibaba Saluja and guides him to a nearby Dungeon. With this newfound friendship, they begin an epic adventure across the world, witnessing various irregularities that seem more frequent than ever.

Holo is a powerful wolf deity who is revered in the small town of Pasloe for blessing the annual harvest. Yet as years go by and the villagers become more self-sufficient, Holo has been reduced to a mere folktale. When a traveling merchant named Kraft Lawrence stops at the settlement, Holo offers to become his business partner if he takes her to her northern home of Yoitsu. The savvy trader recognizes Holo's unusual ability to evaluate a person's character and accepts her proposition. Now in the possession of both sharp bargaining skills and a charismatic negotiator, Lawrence inches closer to his goal of opening his own shop. However, as Lawrence travels the countryside with Holo in search of economic opportunities, he begins to realize that his aspirations are slowly morphing into something unexpected.