Fantasy writers need to solve two problems. They need to create a believable fantasy world significantly different from ours that allows for fantasy elements. But this world and the people who live in it can't be so fantastic that they alienate their audience.
The isekai story offers a neat solution.
'Isekai' is Japanese for 'other world' or 'parallel world'. In this other world, the author is free to dream up societies, fantasy races, magic and other fantastical elements without being hemmed in by such minor things as history or the laws of physics. To create a connection with modern readers, the author plucks a character or a group of characters from the real world (typically 21st century Japan) and plunks them into the parallel world. Adventures and hijinks follow.
At least, that's how it’s supposed to work.
Three Kinds of Isekai Stories
I've noticed three different types of isekai stories: transportation, reincarnation and video game.
Transportation stories involve traversable gateways or abductions. The protagonist may be mysteriously transported to an alternate world by means unknown to everyone. He may discover a portal, accidentally or otherwise, that leads into a parallel world. Or someone from that parallel world forcibly transports the protagonist to that world using summoning magic. Examples of such stories are Now and Then, Here and There, featuring a boy who is transported to a hellish dystopia, and Gate - Jietai Kare no Chi Nite, Kaku Tatakeri, in which a gateway to another world mysteriously appears in Ginza.
In such transportation tales, the protagonist must learn to adapt to his new environment while taking on quests and other missions. Heroes summoned from our world are typically selected to defeat a demon king or some other evil being, and must survive perils and overcome obstacles to achieve his goal. Heroes who pass through a gateway that allows free two-way travel typically serve as a bridge between this world and the other, passing back and forth to exchange or transfer technology, goods and knowledge. More realistic tales have the hero learn the local language and/or the locals learning Japanese; in others, the transportation process mysteriously grants the hero the ability to speak in tongues or the locals mysteriously speak fluent Japanese.
Reincarnation tales involve protagonists being reborn in fantasy worlds, usually retaining or recalling their memories of their past lives. This neatly sidesteps the question of how the protagonist can understand the natives of the fantasy world, since he would have grown up learning and speaking the language. Reincarnated protagonists will tend to use their knowledge to single-handedly spark an industrial revolution, drive themselves towards excellence, or otherwise gain an advantage over others. Moshuku Tensei features a NEET who decides to make the most of his new life after being reborn in a parallel world, while Isekai Tensei Soudouki has a protagonist with three souls in his mind, all of whom use their respective knowledge to build a commercial empire and drag the rest of the land into modernity.
In video game stories, in addition to being plopped into a fantasy world, the protagonist discovers that the world runs on video game logic. Status windows, levels, unique skills, and health and mana points abound. In some stories, the protagonist was heavily involved in the game, perhaps as a player or game developer. In others, the protagonist doesn't have such an advantage. Sword Art Online is perhaps the most well-known of this time, starring protagonists who have their consciousnesses transported to a game world, and quickly learn that death in the game means death in the real world.
As these worlds run on video game logic, realism tends to fly out the window. Either the transportation process grants the protagonist the ability to speak in tongues or everyone speaks Japanese. A person’s ability to fight, craft objects, recover from wounds and other such matters are governed largely by his stats. The transportation process may even grant special powers. Reading video game isekai stories can become the equivalent of reading a role playing game.
Cheat Code Characters
Common to almost all isekai protagonists is that they possess a special power or knowledge after arrival, or the protagonist is already special prior to arrival. These cheats, as they are known in the genre, automatically elevate the protagonist above everybody else.
At the far end of the scale, the protagonist becomes stupendously overpowered early on. In Death March kara Hajimaru Isekai Kyousoukyouku, protagonist Satou is transported to a parallel world based on the game he is developing, and discovers he can cast a meteor shower three times. He promptly utilises the meteor showers to wipe out an army of orcs. In that instant, he hits the level cap and secures useful gear and vast treasures, effectively turning him into a walking god.
At the lower end, in Isekai Tensei Soudouki, protagonist Balud Cornelius shares his body with the soul of Warring States commander Oka Sadatoshi and otaku high schooler Oka Masaharu. None of them have any special powers, but commander Oka is an apex warrior while otaku Oka retains his knowledge of the twenty-first century. Together, the trio accomplish such wonders as inventing shampoo and treating cholera, leaving their mark on the world.
In the case of Gate, Itami Yoji is a First Lieutenant in the Japanese Ground Self Defense Force. He is a mundane human, but behind him is the might of the JGSDF. Through the gate, the JGSDF can funnel troops and resources into the parallel world, allowing them to dominate the land. Thus, the might of the all-powerful Empire easily collapses in the face of modern combined arms, and nigh-invincible dragons fall before explosives and Panzerfaust 3 rockets. Here, modern military technology is the superpower.
A superpowered isekai protagonist, when mishandled, turn the story into a clumsy self-insert power fantasy. The reader can put himself into the shoes of the protagonist and imagine that he is now the lord of the story universe. However, when the protagonist is so hilariously overpowered that nothing in existence can stand up to him, action scenes lose all drama. There is no suspense, no doubt that he will lose, no possibility that he will ever be defeated in battle. Boredom follows.
If an isekai story must have a superpowered MC, there are three ways to get around this. The first is to make the protagonist powerful enough to evoke the feel of a superhero fantasy, but not so much that he becomes a Boring Invincible Hero. Tate no Yuusha no Nariagari, Naofumi Iwatani has unmatched defensive ability, but thanks to the world’s video game logic, he has virtually no attack power and he is still not invulnerable. As he is forced to rely on his squishy companions to do the fighting, there remains the element of drama and suspense.
The second is to reverse the superpowered MC trope: give the protagonist a seemingly useless power, if at all, and force him to make his way in the world. Arifurte Shokugyou de Sekai Saikyou features Nagumo Hajime, a luckless young man transported to a parallel world only to find that he was granted mediocre stats and a useless class. After plummeting into the depths of a monster-filled dungeon, Nagumo must rely on all his wits to survive.
The last approach is to play the overpowered character trope for all its worth. Hellsing got away with starring an immortal and invincible vampire as the protagonist through his force of character. In the case of Jaryuu Tensei, the protagonist is reincarnated as a dragon. In his dragon form, he is so overpowered that nothing his enemies throw at him can do so much as leave a mark on his scales. The story becomes defined by his empathy towards everyone around him in spite of being an evil dragon instead of how he steamrolls over his enemies. While the outcome of action scenes in such cases are preordained, a flashy, cocky or humorous protagonist can inject emotional beats into the sequence, staving off boredom.
What's So Special About Isekai?
What's the key difference between a standard fantasy story and an isekai story? The presence of someone from the real world. Isekai stories need to explore the fantasy world through the lens of the modern-day character. However, handled improperly, the isekai trope becomes a clumsy tool.
In Isekai Houtei – Rebuttal Barrister, Yuuto Shiba is a washed-up wannabe barrister. After he dies in a traffic accident, he is transported to a parallel world. In this world, the god has decreed that the Kingdom of Luanolde shall implement the law of Japan, and that Yuuto shall be a barrister. Quite mysteriously, everyone speaks Japanese (or Yuuto is suddenly fluent in the local language).
Such a forced introduction makes it transparently clear that the author is basically writing Phoenix Wright: Ace Attorney WITH ELVES! Fortunately, the author ensures there is a clash of cultures to fuel drama and make the isekai elements relevant. In his first case, Yuuto must defend a half-elf, in a land that persecutes elves, against criminal charges laid by a noble, whose life and dignity the kingdom views as greater than that of a commoner. Later, he discovers more unpleasantness, such as the actual age of majority in the kingdom, that forces him to use his wits instead of just rote regurgitation of the law.
Without this collision of cultures, an isekai story just becomes a standard fantasy story. The isekai element becomes just a tool to lure in the reader and artificially create empathy.
By contrast the manga adaptation of Tate no Yuusha no Nariagari makes almost no references to Naofumi’s history as a displaced 21st century Japanese male. Aside from the occasional reminder about where he and the other heroes came from, Naofumi’s history plays no part in the story. We do not see him struggling to learn the local language or customs, no confusion over social protocols, no dietary incompatibilities or taboos, no significant employment of modern knowledge and technology, no indication that Naofumi came from a different world. If the Naofumi’s backstory were changed to ‘wanderer from a distant land’ or ‘teenager from the frontier seeking his fortune’, there would be no significant impact on the plot or character. The isekai element here is used simply to justify the fantasy elements, the video game logic, and to handwave Naofumi’s shield and defensive abilities – and even those can be justified using other tropes.
Isekai stories comprise of two key elements: a parallel world with fantastical elements distinct from our own, and a protagonist or protagonists who come from our world. For stories in this vein to realise their full potential, they must balance both halves to create a whole, while avoiding the pitfalls that lead to self-insert power fantasies. Done right, an isekai story shows the reader the best of both worlds.