These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Examples that pertain to the story, Fanon, fandom, or other non-gameplay elements:
Angst? What Angst?: There are a fair number of characters with grim or even tragic histories, and hints that a few others have their troubled sides, but very little angst occurs onscreen (with a few exceptions, mostly involving Mokou), and the tone of the series tends towards carefree.
Awesome Ego: A number of characters are beloved not just in spite of their arrogance, but because of it. Cirno probably tops the list, but honorable mentions include Remilia and Miko.
Broken Base: The fandom will never stop arguing as to what's canon, whether Touhou is canonically grimdark or not, or over popular interpretations.
There's also been some backdraft over the character designs in Hopeless Masquerade, since some people believe they're badly proportioned and they make the characters look too young.
Not to say anything about Ten Desires. The fact that the game is considered easier than the rest of the lot makes part of the fandom simply hate it. The other part can find the bullet patterns nice, even if easy, and appreciate its soundtrack. Needless to say, the first faction can get pretty annoying over the matter.
The Phantasmagoria games probably can cause an even bigger rift in the fandom than Ten Desires. Some say it's the best thing ever happening in the series and want more versus shooters in the series, others shudder at the possibility everytime a new game is announced.
Yukkuris. Some people love them and consider them to be just as much a part of Gensokyo as the girls themselves, while others despise them and think that they're the worst thing that the fanbase has ever produced.
Shou with Ran. Ever since she appeared and was revealed to be Nazrin's master (though not originally), everybody started looking at them as the new Chen and Ran. Both Shou and Ran serve "Old Maids", Byakuren being the latest addition to said group, both are animal youkai and both are masters of a type of youkai you wouldn't exactly expect at first. Ran is a kitsune/fox, the same family as a dog, and her shikigami Chen is a cat. Shou is a tiger, a feline, and her servant Nazrin is a mouse.
Nue with Flandre. Despite their only similarities being the fact that they're both extra stage bosses with bizarre wings and vaguely similar themes, Nue is compared to Flandre, some fans even going as far to call her a rip-off.
Koishi/Flandre is somewhat popular due to the fact they're both odd, hated sisters of a feared woman who own mansions, occasionally depicted as Ax-Crazy.
Covered Up: While Ran's theme, Necro-Fantasy, came first and Yukari's theme, Necrofantasia, was meant as a re-arrange, the latter is vastly the more popular, and Ran's become more associated with Charming Domination (her stage theme) instead. To a certain degree, some fan remixes and covers of the themes and leitmotifs are so memetically popular they overshadow their origins.
Deconstruction Fic: The fandom contains plenty of this; the piles of Fridge Horror regarding the nature of many youkai and their relationship with humans, as well as most characters being selfish, belligerent, and very much insane, provide a lot of material. A Bad End is a Black Comedy take on this.
Designated Hero: Canonically, Reimu tends to be more... cavalier than one might hope from the hero.
Marisa is not really any better either, though she has the benefit of not being as rude as Reimu.
And depending on who you ask, Sanae was falling into this since Unidentified Fantastic Object due to Flanderization of her interest in "Youkai Extermination" and other ditzy tendencies.
Mima of the PC-98 games has become the embodiment of this. Fans wanted her to return to the windows games after so many years.
Shinki is probably the second most popular PC-98 only character, mostly due to Epileptic Trees about her relationship with Alice. (Being a goddess of demons and having a Sakuya Expy as a maid doesn't hurt either)
Flandre, despite only appearing in a few games, is far more well known than her more prominent sister Remilia.
Hong Meiling, Cirno, and Sanae all got primary roles in Hisoutensoku because of their popularity with the fans.
Merlin's Game-Breaking Bug has led to her becoming the most popular of the sisters, exemplified by being the only one of the three to make the character filter in Fanfiction.net's Touhou section.
Since the full release of Ten Desires, Futo has been gaining quite a bit of popularity too.
Hata no Kokoro from Hopeless Masquerade seems to be popular around some circles, considering she is one of the most developed characters in the series (although that's not saying much), her kickass theme, and the fact that the game's story is about her development as a Youkai. She's also the closest the series has to the ever-popular "Emotionless Girl" archetype, though the trope is Played With in various ways.
Double Dealing Character has the Stage 5 boss, Seija Kijin, who has proven to be one of the more dangerous antagonists of the series by being a Manipulative Bastard (by instigating the events of the game and manipulating the Final Boss). Unlike other bosses in the series, she has a Boring, but Practical gimmick that involves Interface Screw. So in a land where "common sense is a weakness" and your power level is decided by how flashy your spell cards can be, she manages to subvert this rule by having one of the lowest bullet counts and still being dangerous.
The lightning connecting the five eyes of YuugenMagan forms the vague shape of a woman. Who is this woman? The real "brain" of YuugenMagan? Someone else, controlling it? Just a coincidence?
Elis. No one is really certain what she is. Vampire? Magician? Demon? The stages preceding her have "Oriental Magician" as their background music... which is otherwise associated with Marisa.
Mima's and Marisa's relationship. There's debate as to whether Mima's her teacher or mother or what. She is generally agreed to have taught Marisa some of her spells, since they have some shared or similar attacks.
Konngara is sometimes thought to be an Oni, as she has a horn, and drinks sake while fighting, like Yuugi would do later in the series.
Fans are divided on whether Rika and Rikako from Phantasmagoria of Dim. Dream are the same person or not. Both are more scientifically-minded than most Gensoukyou residents.
Kurumi may be related to the Scarlet sisters. Her boss theme is called "Scarlet Symphony ~ Scarlet Phoneme".
The relationship between Alice and Shinki (similar to Marisa and Mima above). For that matter, any attempt to reconcile Windows Alice with her PC-98 appearance.
Eirin's character profile says she was surprised to see Sakuya in Imperishable Night, but never explains why.Fanon has explored several possible connections between them, including Sakuya being a Lunarian, Eirin having made her Luna Dial, or the two characters being related in some way. There's also a lot of speculation about how and why Sakuya became Remilia's servant.
Reisen's ears have what look like buttons at their base, which led to speculation that she wears fake ears. However, in Silent Sinner in Blue, the other rabbits in the Lunar Defense Corps have the same buttons too, except for Reisen II, their new recruit. Perhaps the buttons are rank insignia of some kind?
A popular fan theory has Maribel and Yukari Yakumo being the same person. The basic idea is that when Maribel sleeps, she dreams she is Yukari. And when Yukari sleeps, she dreams she is Maribel. It doesn't help matters that they look very similar. Or that both have boundary-related powers. There may be some evidence suggesting she is Yukari's past time-displaced self. Although Maribel is from the future, Perfect Memento in Strict Sense mentions that a note she wrote was found in Gensokyo several centuries in the past. Another common association is with Marisa, again because they have similar appearances and in this case similar first names as well.
Fandom has taken to associating Renko with Reimu the same way they do Maribel with Yukari.
Her name, title, and the fact she has a shackle with a broken chain around her left arm, have all fueled speculations that Kasen Ibara is one of the four Devas of the Mountain - specifically Suika's daughter / lover, if you go by the original legend. Japanese mythology, which ZUN takes great liberties with anyway, does include oni hermits. And that's before you get to her mysterious relationship with the Hakurei Shrine or the thing with her right arm.
Fan Dumb: Specifically, see "Elitism" and "Mad Bride".
A lot of players struggle with the games; do NOT, under ANY circumstances, mention that there are more difficult shoot-em-ups or that there are non-danmaku shooters that are more difficult.
Fandom Rivalry: Many fans of the shmup genre frown upon Touhou and its fanbase, especially Touhou fans who don't play the games. Although, it's rare to see a Touhou fan be dismissive of fans of the genre.
Borderline case for Silent Sinner in Blue. Mainly for introducing two (intentional) God Mode Sues who defeated popular characters in ways that can be best described as either Deus ex Machina or outright cheating.
There's also disagreement within the fandom over how much Inaba of the Moon and Inaba of the Earth counts. It's the only official Touhou production that wasn't actually written by ZUN himself, and some of the characterization differs from his - especially since it's a gag series that plays fast and loose with such things to begin with.
Fan Myopia: Part of this stems from the sheer volume of fan material. Of course, most of the fan material comes from Japan — where Touhou actually is that well-known. This is perhaps why "What anime is this?" is a major Fandom Berserk Button.
First Installment Wins: Averted with the whole series, but played straight with Windows era games, where EoSD, PCB and IN and their casts usually have much, much larger fanbases than the later games.
Freud Was Right: Koishi Komeiji's "Embers of Love" attack, formed of heart-shaped danmaku flying point-first and leaving a trail behind them, looks a little like a different body part. The fandom did not fail to notice, especially since her ability is manipulation of the subconscious.
Love to Hate: Seija. What's not to love-to-hate... she is a Commander Contrarian who uses others to achieve her ends while screwing them over, to begin with. Love to Hate is also something implied by her nature: her feeling is always opposed to that of others, so she falls into self-loathing when she makes people happy and actually prefers it when no one likes her.
Yukari is a slight heroic example. She led a youkai invasion to the Moon and let them get routed... just to teach them that greed and expansionism is bad. And then we have Silent Sinner In Blue. Turns out the whole invasion this time was a distraction so that Yuyuko could steal lunar treasures. Yuyuko found the treasures boring and brought back sake instead, but that still pissed off the Lunarians who were supposed to be protecting that stuff.
Toyosatomimi no Miko set up Buddhism to cow the population, setting herself as something of a holy saint, while actually on the side of the Buddhists' sworn enemies. Countless people died just to ensure that no one can endanger her prospect of becoming immortal. She can give St. Ajora a run for her money.
Fountain of Memes: Spawned an absolutely incredible amount of memes and in-jokes for a single series. IOSYS remixes in particular have a tendency to spawn more.
Watch It for the Meme: Touhou as a whole can claim any number of new fans drawn in by its loads and loads of memes. In fact, because of all the memes, a great number of fans were drawn to the series because of the all-encompassing fandom itself. This odd cycle of fans being attracted to the ever-growing fandom has been described as a "bizarre ouroboros" or a "positive feedback loop".
Moe: Fan depictions of the girls have a natural tendency to play up either the girls' moe-ness or badass-ness. Bonus points if they can pull off both at the same time.
Generally, ZUN tries not to give his characters stereotypical moe personalities, but the fandom will do so in the absence of any canon stating otherwise, such as with Koakuma and Momiji shortly after they were introduced. The guidebooks tend to subvert the moe portrayals by fans, most notably when Symposium of Post-Mysticism showed Kisume to be a Creepy Child.
Ron the Death Eater: Sanae's newly discovered interest in youkai exterminationnote Where "extermination" really just amounts to ritualized playfighting has led to fans taking it a bit far and giving her a sadistic streak and a fanatical zeal for it.
Alice gets turned into a creepy loser who murders her lovers or love rivals often, for whatever reason.
Koishi is turned into a psychotic murderer by fans who take "subconscious reading" as a very bad thing.
Byakuren is often either depicted as a naive loony or a genocidal murderer. Or both. Mostly from suspicion that people who try to be good aren't, and further exacerbated by SoPM and the fact that she sides with youkai against humans and dodged several questions from Miko.
Self-Fanservice: One important reason for Touhou's popularity is how ugly ZUN's original character art is, inspiring legions of fan artists to improve it. As alluded to elsewhere, he seems to have trouble drawing a girl who looks postpubescent, leaving fans to come to a consensus on what some characters should "really" look like. In a broader sense, the entire series itself has next to nothing resembling sexual or romantic content, but you would never guess that from the fandom.
Since he's almost the only straight option in Gensokyo, there are a lot of crack pairing pictures with Rinnosuke and one of the girls. Somehow, a few fans even manage to slash him despite the rather limited options. The most common person he is slashed with? ZUN.
Wriggle is often paired up with Yuuka, of all people. Fridge Brilliance kicks in once you realize that Yuuka's power is tied to flowers, Wriggle is a firefly, and flowers rely on insects to pollinate.
Mokou and Mystia, in spite of (or perhaps because of) Mokou claiming to run a yakitori stand. Though Mystia is a sparrow, not a chicken.
Sibling Incest: Any pair of sisters will have fanart showing them in a relationship.
Spoil At Your Own Risk: ZUN specifically requested that the endings to the games not be posted on the Internet to avoid spoilers; fan sites have managed to follow this request, but once in a blue moon, the content will pop up somewhere. Generally though, if you're looking for the ending, you'll be able to find it.
Unfortunate Implications: In Symposium of Post-Mysticism, Akyuu notices how her three interviewees are, in one way or another, "recent immigrants to Gensokyo". She also notices that the only thing preventing them from making problems is the tension between them. The interview ended with the interviewee being chased away by Reimu — the face of the establishment. The worst part: all three interviewees are religious hardliners and they seriously consider fighting each other, even if it will imperil Gensokyo!
Values Dissonance: Something not readily apparent to western viewers. Byakuren was originally motivated by fear, then love (the two extremes) and used deception to make youkai and humans equal. She's an extremely lapsed Buddhist. The Japanese are also critical of the western take on "equality". If you treat the strong and the weak the same way, the strong will have an advantage. Needless to say, quite a few grimdark doujinshi turn her into some sort of evil mass murderer who genocides "weak" beings.
The same goes for Miko, who is similarly lapsed: Taoism is about letting things be, not actively meddling in everything.
Viewer Gender Confusion: Meira, Wriggle and Shou are sometimes mistaken for males by the fandom. Wriggle wearing pants and a tomboyish look could easily be mistaken for a boy at first glance. In Shou's case, her masculine-sounding name and appearance didn't help things either.
What an Idiot: On Easy difficulty, Cirno's Icicle Fall spell card has a blatant blind spot right in front of her.
Cirno. Though some might argue she has it coming, she is treated rather harshly by other characters, particularly in Hisoutensoku when a purposeful misdirection by Marisa nearly gets her killed. As much as a fairy can be killed, at least.
Hong Meiling gets this in fanon a lot, especially by making Sakuya out to be abusive.
Flandre. Willingly or not, enduring almost complete solitary confinement for several centuries is not known to have many benefits, while her ability ensures that even at best everyone will always keep her at a metaphorical arm's distance.
Yuyuko. Though she is much better now, the circumstances that led to her becoming a ghost, as well as the desire to resurrect the person under the Ayakashi because she could only bring death and never life, fall well into this trope.
Reisen. Often played for comedy in fanon. Possibly of the iron variety due to her desire to protect her masters and subordinate despite how they treat her.
Kogasa. She's an unwanted umbrella who can't even use her power to surprise people properly. In Double Spoiler her title is "Pitiable Illegally Dumped Object". And for Ten Desires, it's "Greatly Troubled Lost Article". There, she's seen trying to get the help of the protagonists, as she can't deal with that stage's boss. And then the protagonists beat her up anyways. Fanart often takes it to Butt Monkey status, sometimes even going so far as to put her crying on a pile of trash while dressed in tattered clothes.
Byakuren, even more so than Flandre, though definitely of the Iron Woobie subtype, remaining dedicated to her self-imposed mission.
Your Cheating Heart: Marisa Kirisame of is a noted Memetic Sex Godess, and has been shipped with virtually every character she's ever teamed up with, plus other characters like the protagonist Reimu, The One Guy Rinnouske thanks to him being a part of her childhood, and Enfant Terrible Flandre. Thanks to this rather large "harem", and her Kleptomaniac Hero status, she's often portrayed as sometimes outright taking her friends and lovers completely for granted. A meme revolving around her is even called "Marisa Stole the Precious Thing", based on a comic where Patchouli saying that Marisa stole a spellbook from her was misinterpreted to mean that Marisa stole Patchouli's virginity, setting Alice off on a jealous rage against Marisa before she could hear the full story, and later an IOSYS song by that title.
Examples in the games' gameplay:
Breather Level: While the final bosses are devastating, the final stage tends to be mercifully short, often with enemies that drop full powerups. Reisen is infamous for being one of the easier stage five bosses.
Marisa in Mountain of Faith. Her B-type shot has a glitch that makes it insanely powerful under the right circumstances, earning it the Fan Nickname of MarisaBugged.
Much less severe, but Marisa's teamup with Alice in Imperishable Night has access to another highly damaging exploit, which fans have dubbed the Malice Cannon.
Sakuya's A-type shot in Perfect Cherry Blossom is considered this by some since its unfocused mode covers the top of the screen, while the focused concentrates it entirely on single target and is homing withing a relatively wide angle. She also has four bombs per life with the same properties.
MAlice Cannon in Imperishable Night. Lasers in the earlier Touhou games were somewhat laggy in their hit detection. In IN's case, this meant that you could switch between Alice and Marisa rapidly, and Alice's full damage would go through, the lag on the laser covering the time as Marisa.
Marisa B(ugged) in Mountain of Faith. Whenever Marisa B has between 3.00 and 3.95 power, the central laser does ten times the appropriate damage value when unfocused.
In Subterranean Animism, Reimu C (Reimu and Aya) and Marisa B (Marisa and Patchy) can destroy the 3rd (only in the demo, she can't be destroyed in that way in the full version), 6th, and extra stage midbosses just by bombing them as they appear.
The tenth game, Mountain of Faith, generated discontent among fans because of the significant gameplay changes, such as linking the bomb system to weapon powerups, not having individualised bombs for each of the shot types, and making the continues send you back to the beginning of the level. Most notable was the removal of the "graze" system, where one is rewarded for getting close to bullets as often as possible without getting hit. This was thankfully put back in for Subterranean Animism, where's it's actually the basis of the scoring system.
Undefined Fantastic Object heralds the return of more classic features, such as the separate bomb bar and character-unique spell cards, but the UFO mechanic for this game proves annoying to many players, especially since using said mechanic is one of the few ways to gain more power, bombs, points, and lives. And by "one of the few" we mean "basically the only really effective way."
The scoring system in Ten Desires requires that you spend most of the time near the top of the screen, meaning you have to rely on luck and memorisation to avoid getting hit, rather than skill. The game also gets rid of the deathbombing, another hallmark of the Touhou series.
Deathbombimg is actually possible in Ten Desires. It just has what is probably the most sadistically small time frame ever for it in the history of Touhou. You basically need to have an instance of Super Reflexes to do it, by predicting your death and bombing just as you're hit. Otherwise, you'll just enter Trance mode (if applicable) and die.
Players familiar with fanworks come into Cirno's fight expecting it to be a joke. Then they eat icicle shotgun. And, while Icicle Fall ~ Easy deserves its memetic status, the version on normal is actually fairly nasty. It's basically the same thing, except Cirno also fires a spread of larger bullets in front of her, meaning you actually have to navigate the icicles, which is harder than you'd think.
Utsuho in Hisoutensoku is a Skill Gate Character with extremely powerful (and surprisingly quick) melee attacks as well as immense and incredibly dense strong bullets. She's also one of the more popular characters, making her the bane of most players just starting out.