That Time I Got Reincarnated as a Slime is an isekai light novel, manga and anime series showcasing a fun and colorful world populated with lovable characters. Some of the plot is self-explanatory, since, yes, the hero is someone reborn as a humble blue slime critter in a fantasy world, but a lot more happens from there. Before jumping into the now-airing second season, here's everything you need to remember from Season 1.
Rimuru's Mission Of Unity
37-year-old salaryman Satoru was on the wrong end of a knife attack in the streets of Tokyo. As he lay dying, a strange voice informed him that he was gathering magical abilities and strengths, based on the complaints of his dying body. He was bleeding out, so his next body wouldn't need blood. He felt powerless, so he'd obtain a Predator skill. But what did that mean? Seconds later, Satoru awoke as a blue slime in a cave, with only the "Great Sage" for company. He experimented with his body and learned to see, then met the great dragon Veldora, bound by the Hero's magic. They struck a deal, and Rimuru ate Veldora's body with his Predator skill. Once Rimuru gathered enough skills from other cave denizens, he ventured into the world.
The Jura Forest is a place of fierce competition and natural selection, but Rimuru Tempest didn't subscribe to those rules. He befriended a village of goblins, then helped them fend off a huge pack of dire wolves. Rimuru peacefully united the two tribes into one and named everyone there to help them evolve. One tribe at a time, Rimuru made new friends and added new species to his growing coalition, making use of every group's unique skills and abilities. The goblins were just the start: the tempest wolves served as faithful companions and transport, the dwarves were master craftsmen and carpenters, the lizard-men could farm in hostile environments, the ogres (now kijin) served as elite guards and even the piglike orcs joined as manual laborers, building roads and large buildings. Rimuru was swelling with pride as his new nation of benevolence and tolerance took shape, and unlike other isekai protagonists, it never even occurred to him to try and form a harem, even though he was popular enough to get one.
Established kingdoms such as Blumund, Ingrassia and the armed dwarf nation of Dwargon took notice and became wary of the Jura Tempest Federation. The dwarf king paid a visit and established diplomatic ties with the Federation, and the kingdom of Blumund followed suit, including the establishment of free trade. The Federation was really putting itself on the map, but that wasn't Rimuru Tempest's only project -- he also wanted to fulfill Shizue Izawa's wish.
Shizu And Her Students
A wandering hero known as Shizu (real name: Shizue Izawa) crossed paths with Rimuru early on. Just like Rimuru, she was reincarnated from real-life Japan. She'd been summoned at the hand of Demon Lord Leon Cromwell, who had placed the fire spirit Ifrit into her. Shizu eventually met and replaced the masked Hero, and Shizu took on a few students in Ingrassia. But her time was running out, and she allowed Rimuru to eat her to bring her peace at last. Rimuru could now assume Shizu's likeness, and he and his wolf friend Ranga departed for Ingrassia to find Shizu's students. They were currently enrolled at Freedom Academy, as part of the Free Union of adventurers.
Shizu's five students were also isekai summons, and if something wasn't done soon, these kids' intense magic would overwhelm their bodies. Rimuru gave his five new charges some basic training and instruction, then ventured to a spirit realm and gathered powerful spirits to place into their bodies, with the aid of the Queen of Spirits, Ramiris. After all, Shizue had survived since Ifrit managed her intense power, so surely the same would work on the five children. As hoped, spirits with differing powers arrived and placed themselves inside the five students, but Rimuru noticed that the spirit which possessed the girl Chloe was different from the rest. It resembled a dark-haired woman, not unlike Shizue and the Hero before her. Perhaps the Hero would be reborn in Chloe?
Next, Rimuru sent his students on a practical exam, journeying to a cave to retrieve a magical item while competing with students from other classes. It was a rough trip since a butler from the local nobleman's house revealed himself to be a powerful demon, but Rimuru's assistant teacher, Tiss-sensei, helped the five youngsters confront this threat and vanquish it, and pass the test. Now, Rimuru's tenure as a teacher is nearly up, and Tiss-sensei will handle the kids' education from here.
However, Shizue once had another student named Hinata Sakaguchi, now a grown woman and the captain of the Holy Knights. She blames Rimuru for Shizue's death, and before long, she will come face to face with her beloved teacher's "killer" with lethal intent.