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.

Taking a break from his time as a teacher, the powerful slime Rimuru Tempest returns to his kingdom, eponymously named Tempest, just in time to begin negotiations with a nearby nation—the Kingdom of Eurazania. While the negotiations are anything but peaceful, they do end successfully, allowing Rimuru to return and finish teaching. When trying to again return to Tempest, this time permanently, Rimuru is stopped by a mysterious figure who is somehow able to constrain the many magical abilities he has at his disposal. In Tempest, the situation is even worse. A group of unknown humans has invaded the land and are assaulting its citizens, both influential and innocent. They are not just trying to bring harm either—they have the intent to kill. Can Rimuru overcome his powerful and dangerous foe and return to Tempest before it is too late?

The nation of Tempest is in a festive mood after successfully overcoming the surprise attack from the Falmuth Army and the Western Holy Church. Beyond the festivities lies a meeting between Tempest and its allies to decide the future of the Nation of Monsters. The aftermath of the Falmuth invasion, Milim Nava's suspicious behavior, and the disappearance of Demon Lord Carrion—the problems seem to keep on piling up. Rimuru Tempest, now awakened as a True Demon Lord, decides to go on the offensive against Clayman. With the fully revived Storm Dragon Veldora, Ultimate Skill Raphael, and other powerful comrades, the ruler of the Tempest is confident in taking down his enemies one by one until he can face the man pulling the strings.

Pokémon are peculiar creatures with a vast array of different abilities and appearances; many people, known as Pokémon trainers, capture and train them, often with the intent of battling others. Young Satoshi has not only dreamed of becoming a Pokémon trainer but also a Pokémon Master, and on the arrival of his 10th birthday, he finally has a chance to make that dream a reality. Unfortunately for him, all three Pokémon available to beginning trainers have already been claimed and only Pikachu, a rebellious Electric-type Pokémon, remains. However, this chance encounter would mark the start of a lifelong friendship and an epic adventure! Setting off on a journey to become the very best, Satoshi and Pikachu travel across beautiful, sprawling regions with their friends Kasumi, a Water-type trainer, and Takeshi, a Rock-type trainer. But danger lurks around every corner. The infamous Team Rocket is always nearby, seeking to steal powerful Pokémon through nefarious schemes. It'll be up to Satoshi and his friends to thwart their efforts as he also strives to earn the eight Pokémon Gym Badges he'll need to challenge the Pokémon League, and eventually claim the title of Pokémon Master.