Anime covers a wide swath of genres, from comedy and romance to horror, action, science fiction, and some anime shows that are simply beyond definition. Meanwhile, a popular type of fantasy anime is the isekai genre. In it, an ordinary person will find themselves in a fantasy world, and they may or may not be able to return home! Think of it as anime The Wizard of Oz.
Two popular isekai series are The Rising of the Shield Hero, and That Time I Got Reincarnated as a Slime. In each one, a man finds himself in a fantasy realm, and he's got some work to do. In Shield Hero, Naofumi bears a shield in combat and must help fight off Waves of monstrous invaders. In Slime, a businessman is killed, then is reborn as a humble slime creature and uses his newfound powers to build his own nation. Why might either one of these anime be the best isekai out there right now? Let's break it down.
Update July 13th, 2020 by Louis Kemner: As of this writing, the isekai animated series Re:Zero: Starting Life in Another World is one of the most popular streaming anime series, and fans have been eagerly looking forward to its return for some time. This is ample evidence that the isekai genre is alive and well, and perhaps it's time to reassess Shield Hero and Slime and figure out which is truly the best isekai series out there, and why. Both have a lot of merit, after all.
15 Shield Hero: Best Girls
Most anime shows have a Best Girl, who may be the most wholesome, kind, attractive, and heroic young lady in the franchise. Shield Hero has two very strong contenders: Raphtalia, and Filo. On the left is Raphtalia, a humanoid lady who was bought as a slave, but was freed to become Naofumi's loyal sword maiden.
On the right is Filo, a bird-girl hatched from an egg who at once designated Naofumi as her mother hen! Both are tough, brave, and kind girls who won over the audience's hearts with ease.
14 Slime: Building a nation
Anyone who has played Sid Meir's Civilization games knows how much fun it is to build a nation and watch all the pieces come together, one by one. A sprawling empire can start from a single camp and a charismatic leader.
In Reincarnated as a Slime, Rimuru Tempest makes peace between a goblin village and a wolf pack and, from there, he keeps adding more citizens of different races to build a whole city, block by block. It's very satisfying and inspirational to see a new, tolerant city rise from nothing.
13 Shield hero: A resourceful lead
Naofumi, the star of The Rising of the Shield Hero, has his work cut out for him. He's meant to work with the other three heroes, but he was soon falsely accused of a heinous crime and cast out! But that didn't get him down.
Naofumi doesn't need incredible magic powers to save the day, since he's meticulous, resourceful, and clever, and he sees a route to victory where anyone else would see defeat. Even by himself, he rescues villages and townsfolk more resourcefully than the other three heroes. It also helps that Raphtalia and Filo are lending him their services.
12 Slime: Diversity is strength
Anime is well known for its positive messages, often about courage, hope, friendship, and changing the world for the better. In the case of That Time I Got Reincarnated as a Slime, the main character, Rimuru Tempest, uses his incredible magic and foresight to unite the Jura forest's many races into one nation.
Rimuru never wipes out a village or commits genocide, even against pig-like demons. He ends wars with minimal bloodshed, then welcomes the losing side into his growing nation! Every time this happens, Rimuru's kingdom grows ever more powerful and diverse, thanks to the skill, knowledge, and wisdom of each race incorporated. After a point, Rimuru's city is like an isekai New York City.
11 Shield Hero: The wave battles
It's true that Slime has some really cool boss battles (more on that later), Shield Hero has a better sense of urgency and tension with its Wave battles. This sunlit fantasy world has a problem. As prophecies foretold, a series of Waves will thrust monstrous invaders in the realm, and the very sky turns red as freakish monsters emerge from portals to launch attacks.
Each Wave is deadlier than the last, and Naofumi can tell that at this rate, he may not survive the next one. And those Waves have a knack for striking at the most inopportune moment!
10 Slime: Rimuru is very kind
While Naofumi is a tough and resourceful guy, Rimuru Tempest wins over viewers because of his wonderful personality and positive worldview. The tolerant and diverse city is possible through the lead character's own kindness and acceptance of others, and he impresses this idea on his followers time and again.
He's an optimist, being certain that every person should have a place to call home. No problem is impossible to solve, as far as Rimuru is concerned, and he's won some battles many other people thought unwinnable. Plus he's an agreeable and upbeat fellow anyway, adding to his charisma. It's no wonder that goblins, wolves, ogres, and more all follow him!
9 Shield Hero: It's gritty
Slime is an upbeat and really funny series, while Shield Hero may feel more like The Lord of the Rings. Some anime fans may prefer that, and Naofumi finds himself thrust into a damaged world that faces total extinction from the deadly Waves.
Naofumi faces darkness such as the slave trade, disease-ridden towns, prejudice, and more, and this can make for an engaging watch. Finding yourself in a new fantasy world isn't necessarily going to be fun, but at least Naofumi is tough enough to survive. And this grim setting makes Naofumi's acts of heroism and kindness all the brighter.
8 Slime: Great magic systems
Yes, Shield Hero shows plenty of magic, but Slime turns it up to 11, and it's thrilling to watch. Rimuru is no ordinary slime creature. He can devour any object or animal to learn its properties and replicate them, and that gives him a huge grab-bag of powers.
Rimuru can spin metal spider-webs, conjure devastating black fire, make magic potions, shapeshift, and even print books with his own body! His skill set is as diverse as his nation is, and this makes him a flexible and creative fighter. Not only that, but he can produce medicine and tools at will.
7 Shield hero: Proving himself right
While Naofumi is a resourceful and righteous hero on his own, the other three heroes are not so keen to join him. They see him as a thug and outlaw, due to a smear campaign that got him exiled to start with. Several times, though, Naofumi crosses paths with the other three heroes, and they start to cooperate.
This makes them much better in combat, and the bow, spear, and sword heroes are quite impressed with what Naofumi can do. Best of all, the three other heroes later learn of Naofumi's innocence and formally welcome him as a comrade. It's a big relief when this happens, and vindicates Naofumi's efforts.
6 Slime: Bosses and monsters
What sort of enemies does Rimuru fight? More like, what doesn't he fight? Rimuru's first battle is against a bloodthirsty pack of wolves, where he uses metal threads to kill their leader and end the battle in a draw. Rimuru also faces a fire-slinging djinn creature, and he clashes with Geld, the massive demon overlord. Don't forget that time he dueled the ogres, who later joined his side.
Rimuru also did battle with the powerful demon lord Milim, until they settled on a draw and Milim became a friend of sorts. All of these battles are fantastically animated and great fun to watch. So many scary monsters out there!
5 Shield Hero: Good Morals
At first, Naofumi is actually supporting the slave trade by buying Raphtalia. But he doesn't keep that up for long. Raphtalia grows up fast, and she's ready to strike back against the monsters who enslaved her village years ago. Naofumi is right behind her.
Naofumi's party takes down the nobleman who orchestrated the capture of Raphtalia's friends and family, and they free the survivors who remain. Now the villagers are free to build their own future at last.
4 Slime: Teaching A Class
Rimuru Tempest is an isekai hero who fights to uplift others and give them a future, not to build his own personal empire or have fun exploiting his vast powers. Shizue, the previous isekai hero in the world, died and left behind a class of several young students.
When able, Rimuru visited them at Freedom Academy, and made it his mission to cultivate their potential and give them hope. He even found a way to stabilize their powerful magic and thus extend their lifespans in time for their first major test.
3 Shield Hero: Cool Beach Episode
Many anime shows have a beach episode, and even a gritty isekai series like The Rising of the Shield Hero has one. Naofumi's gang visits a charming, sunny island for a well-deserved break, but of course, there's something afoot.
Raphtalia and Filo dive under the water to explore the ocean, and they find a huge, mysterious temple down there. The hunt is on, and Naofumi joins the girls down there... only to find another hourglass that warns of the next Wave. This bodes ill.
2 Slime: Great Characters
Some anime characters are more deeply realized than others, and That Time I Got Reincarnated as a Slime has characters who may not yet have deep backstories, but they do represent every good aspect of the isekai genre.
Milim, pictured, is a powerful demon lord who subverts the very idea of a great demon overlord, while Shion is a bumbling and lovable character with nerves of steel in combat. Shizue, meanwhile, is a selfless and kind-hearted woman who set a great example by giving her life to Rimuru to help him train her students.
1 Shield Hero: Consequences
A strong theme in this series is the idea of consequences. Any time the hero or any other powerful character acts out, there may be negative results, and the character must be held accountable. Unlike in some other isekai series, Naofumi and the other Cardinal Heroes must deal with what comes after the battle, too.
The Bow and Sword heroes learned this more than once, and Naofumi had to clean up their messes. In addition, Naofumi is making a lot of enemies during his quest, and he'll have to face them all sooner or later. He's not the type of hero who just topples the bad guy and wins everyone's adoration; he has to do everything right. That's a lot of pressure.