How Plex manages this category is ridiculous. It doesn’t exist in TMDB so I guess it’s created by the Plex Agent. I’ve 304 Anime movies in my library and it’s only picking up 50! I’ve like 10 One Piece movies and the Anime Category is showing just 1.
Either the Plex agent does it job properly or this is implemented: Feature Request: File Path filter // Automatic dynamic Full Pathname tags & associated Filter - #32 by aschnt
ANIME = ANY ANIMATION COMING (EXCLUSIVELY) FROM JAPAN
TMDB doesn’t use it for genre but it does for keyword. TVDB and IMDB do use it for genre and Plex also pulls from those sources so might be where it picks it up sometimes. I know my movies sometimes have it and sometimes don’t. I add it manually to the Genre tags if it doesn’t pick them up - sometimes it does sometimes it doesn’t. It can be hit or miss but what is “anime” can get contentious.
I mean - is Avatar The Last Airbender anime? I only mention that one because it’s a common example due to its mixed release and style. Is Anime only Japanese produced animation? Is it a style that changes over time but includes similar tropes\cues and isn’t always made for Japan audiences how do you define it each time? That’s why some sites kinda shy away from “anime” as a genre tag.
Plus anime is more of a medium than a genre - a medium that is covered by the broader “animation” which is again not really a genre on its own but serves to help define a style. Saying something is anime or animation tells you nothing about the type of movie it is, just that it’s not live action. Spirited Away and Mars Express and Snow White and Ninja Scroll are all “anime” or “animation” but none of them would be grouped together if they were live action movies.
Anime has always been kinda problematic to categorize and manage - who else but anime fansubbers do Hi10p with SSA subs - that it’s just one of those things that takes a bit of manual handling.
Plex used to have 3rd party agents you could install that would link to Anime specific sites for library management - like AniDB and such - but I don’t think that’s an option anymore. Emby and Jellyfin do have those plugins if you really want something that’s more flexible specifically for Anime.
Well, the idea of using something like this is to automate the work, I’ve to add genres manually I can also organise the library myself and ditch Plex altogether 
Avatar The Last Airbender anime? No!! 
Is Anime only Japanese produced animation? Of course!!
I agree, to me anime is a category not a genre, but that is what the world gives us to work with.
SSA subs are superior to SRT, but as long as the US prefers dubbing the ■■■■ out of anything instead of consuming media in its original form, we’ll have issues with subs everywhere, like it’s the case since the dark ages of the Internet.
Emby is another pitfall. Jellyfin is great but doesn’t provide a relay serive, ergo, useless for the usage I need.
Thanks for replying friend 
As you’ve represented yourself, anime fans can have very specific expectations on what is or isn’t “right” about aspects of anime. 
That also makes it tricky to automate this stuff in a way that matches everyone - particularly between old school and new school fans I suppose; that’d be a whole other thing and I’m not taking any particular sides here… but just pointing out that one person’s “of course!!” is another person’s “No!!”. Anime is just kind fractured in a way that nobody will ever be happy no matter what automation is done. TMDB\TVDB folks who help manage those metadata sources argue over it all the time.
Heck when anime started showing up on video rental store shelves we had a hard time putting them out appropriately since “animation” was often mixed in with family videos and some of these were NOT family friendly at all… again, that’s a whole other thing.
As an alternative solution, you could put Anime in its own Library. That’s what people did when they setup dedicated agents (like HAMA) and I do that with my Anime shows today (but not my movies - I just manage the genre tag as I add content). Typically Plex recommends not breaking out libraries much but I’ve gone back and forth and settled, for now, on separate libraries for shows working well. If you have a dedicated Anime library for movies and for TV you can also make collections that will cross types so your Macross TV collection will link\display your Macross Movie collection (just name them exactly the same). That can make it easier - not perfect - to keep those mixed media series linked.
I struggle with this “is it Anime?” question as well. I started to lump in Chinese/Korean anime, because if I couldn’t tell it wasn’t Japanese without looking at the cast, then it is anime. There are quite a few series that just blend in, such as “To Be Hero X” and “Link Click” that I had no idea on.
So I just generally go “was it asian-created?” or “Would person ‘X’ want to watch it?” (X is a family member who has a distaste for anime). If so, it’s anime.
As Insomnic_1 says, I split out my anime into dedicated TV show and Movie libraries. For shows, it rivals my non-anime library in size and count, so it’s nice to have a reduced list of content when browsing for something to watch.
It’s all about expectations…
Are those Anime?
In particular in the west … where audiences grew up on crippled versions of Anime to make it more kids friendly, e.g.
„Nausicaä of the Valley of the Wind“ cut 22 minutes short in the 1980s and released as „Warriors of the Wind“.
Good times 
Yes, and… Huh. I have seen the Maya movies, but not the show. Based on the movies, I would have slotted the show into my regular anime section.
Interestingly, I remember growing up watching and rewatching the 80’s Voltron show, or at least the pilot episode, which was kind of movie length. Up until a decade ago, I was SURE that it was an American cartoon. From then up until literally minutes ago, I was SURE that it was a Japanese anime. Turns out, it was an American only licensed product from Toei, so I would be forced to slot it into my non-anime category.
Looks to me like another case of editing a product to make it more “appropriate” for a foreign market. Just like the original Macross vs Robotech, and Space Battleship Yamato becoming the edited Star Blazers.
Whether the Americanized versions are still anime or not is debatable, but the animation at least is still from Japan and stories are based on the original plots.
As far as the OP’s actual problem…
You’re just not naming your files right.
You haven’t listed what One Piece movies you specifically have, but if they are not matching I hazard to guess they are not considered “movies” by the TMDB so they don’t have entries. Or at least no one has made movie entries for them, TMDB is a crowd-sourced database like theTVDB, someone has to go through the work of making the movie entry for Plex to match it. They are probably listed as Specials of the TV series. Really I think listing them as TV Specials is better for some shows, like One Piece, because then if you watch the show the films are played back naturally when they come up in release order. You don’t have to remember to “watch season 1-3, but then this movie, before you see season 4, and then this film and this film…”. If the programs are all there, and this is about the movies not being listed under the “Anime” category on the cleint, those categories are set from the Genre tags on the movies, which is also info pulled from the TMDB, so they are missing the category there, too. You can just add them yourself to your server listings for them.
That feature request is bad imo, because it goes against Plex as a concept, which is to abstract the files themselves from how you curate and consume media. You shouldn’t need to change directory or file names to alter a smart playlist. The first two replies on it exemplify why the request isn’t good, it’s brought up by people who really just want Plex to work with their preexisting bespoke methods of organizing media, when the point of the file structure is to allow Plex to accurately identify the type and content of media files, even if they are tagged incorrectly in their own internal metadata.
Having to make naming adjustments to files for them to be picked up right is annoying, especially if it goes against your personal feelings regarding how the media exists in the franchise (for anime especially, since most sequels are considered separate shows and not additional seasons of the first series). I recommend using theTVDB for show ordering for these shows since you get the option of DVD and Absolute ordering then at least (and supposedly TMDB program groups are coming too, in the future). One always has the option of having them not matched by Plex, and just filling in the information manually, too.
Oh shoot, so it is. I glanced at the wiki for the show, and only saw American names all over it, even the production. Now, I notice:
The series is an adaptation of the Japanese super robot anime series Beast King Go-Lion, which was dubbed into English and edited to create Voltron episodes.
Hmm, interesting. I’m sure if I had Power Rangers, I’d say that is a US show, even if the combat scenes are taken from a Japanese show. Guess I’ll keep this in the non-anime folder for now.
If it’s the English-language American version I think that makes sense, too. I don’t think I would list Robotech in an Anime library if I had that version. Now that this has been brought up, I remember I overwrote the title on Star Blazers because the TVDB entry was more written for the American adaptation and there was no separate listing for “Space Battleship Yamato”. 
I should revisit (and maybe Fix Match) that now…
I’ve never understood how plex gets its anime categories. Usually this stuff is scrapped from imdb, tmdb or tvdb. I’ve only with 68 movies with what plex considers anime including such anime classics as Robin Robin and excluding Adieu Galaxy Express 999 its just a mess so I just ignore categories altogether.
Furthermore, 17 Dragon Ball Z movies and 26 Pokemon movies all bar 2 of which plex does not consider anime.
I think part of the problem is anime is a medium and not a genre, which is what Categories is geared towards. Even declaring a title as “animated” can be a judgement call since there are works that blend live action and animated sequences, plus productions that involve cooperation on both sides of the ocean.
I’m rewatching Disney’s Gargoyles right now, and recently found out that the first two seasons were made at Disney’s Japanese animation studio and 13 episodes were directed by Saburo Hashimoto, who has been involved in Dear Brother, Aim for the Ace, The Castle of Cagliostro, and Yatterman among other anime and western cartoons.
Agreed.
Wow, I have been ignoring the “Categories” menu option that appeared months (years?) ago, so I wasn’t referring to the “anime” category, just my own struggle with self-categorizing these.
Examining my “anime movies” library, I have 238 movies, but only 73 are in the anime category. Batman Ninja is not anime, but Batman Ninja vs. Yakuza is. None of the Appleseed are anime. 
More interestingly, in my “animated movies” library, 8 are so-called “anime”. 1 is one of many DC Animated movies, but none of others are here. Robin Robin is here (REALLY?). And only one of my 10 Boonie Bears (Chinese movies) is considered anime. Of the rest, 3 are definitely American movies (LOTR, Witcher), one is a dub of a Russian movie, and one is a dub of a Japanese movie.
Ironically the Categories screen is just an easier-to-access version of the genre filter that has been available on the Library view forever. They cooked it up because people were ignoring it there too, I guess.
I don’t find it that useful because of redundant categories and there are movies listings it’s a real stretch to agree with or are trolls (Happy Sugar Life is a “Family” show? Uh…)
Funny enough, I’m hitting exactly the same ~31% average. My Anime Films and OVAs library is 332 titles after expanding collections, only 102 of which are being categorized as “anime”.
