Across genres and target audiences, the anime industry as a whole has several tropes. One of the most common is amnesia, with the main character or secondary protagonist losing their memory before the events of the series. While this storytelling mechanic might seem trite, there are actually a few good reasons for it.
Amnesia allows viewers to learn about a series' world at the same time as the characters, making the protagonist something of an audience insert. Likewise, it's a way to add a central mystery to the storyline, quickly giving the plot a sense of urgency. Here's a closer look at why anime, no matter the genre, uses amnesia as a plot device so much.
Amnesia Makes Anime Characters More Relatable
The examples of anime using amnesia to develop its cast are many, including the infamous Elfen Lied, Eden of the East, the fittingly named Amnesia and arguably, Dusk Maiden of Amnesia and Golden Time. In the case of the latter, it involves a young man who enters adult education after having lost much of his memory in an accident. One of the other characters in the series is an old friend of his who blames herself for his trauma. This all allows viewers to receive this information before he does, adding tension and conflict to a series that's otherwise a fairly standard slice-of-life anime.
Amnesiac protagonists become characters that audiences follow in more ways than one, as they learn about the world of the anime at the same time that viewers do. Likewise, they're charmed, shocked or angered by the actions of others at the same time as viewers, giving a show an air of authenticity and relatability. These types of stories are told across various genres, be it a realistic series or a fantastical adventure. The ubiquitous isekai genre has examples of this, with the virtual classic .hack//SIGN having a character who knows they're in a video game world but has no knowledge of their previous life. This presents another big reason as to why amnesia is used so much in anime.
Amnesia Adds a Quick Tension to an Anime
Whenever it's established that an anime character has amnesia, the driving plot involves them getting their memory back and discovering who they were beforehand. Even if it isn't focused on much at first, it presents a direction for the plot to travel later on down the road. One example of this was the iconic card-battling series Yu-Gi-Oh!, in which Yami Yugi's backstory wasn't revealed for the longest time. The only knowledge of his past involves his adeptness at games, but the full nature of his origins wasn't revealed until the end of the series.
Other titles, such as the aforementioned Eden of the East, have the protagonist starting off realizing that they can't remember who they are or how they got into their current situation. Thus, them finding out the truth about their path is the main part of the storyline and not merely something that's pushed off until later. Of course, amnesia isn't a plot point exclusive to anime, and it's quite common in other mediums, as well. Just as in those cases, it can be used to derail the story by robbing an important character of their memory and identity. This can result in the culmination of their character development theretofore, with the other cast members having to remind them in some way of who they once were and where they came from.
Given how well-trodden yet dependable the plot point is, it's unlikely that amnesia will ever be gotten rid of as a storytelling element. It might not be the most original way to add drama and make characters relatable, but for certain genres, it fits perfectly. Considering how well it's been utilized in some productions, it's hard to forget what an amnesiac protagonist can offer an anime series.