I am finally back. Time to reply...
Important distinction between suggestive or fanservice-y and you know, zorn, that's why I didn't know if the chart was relevant. The former usually doesn't get the R-18 tag.
Sure, there is indeed a difference between the two. However, the difference is at time so shady you no longer know whether to place some one way or another. As for suggestive not getting the R-18 treatment, I guess there is a limit of how suggestive it can be? But this reminds re of the discussion on gacha/anime art in general, with the whole "totally not NSFW/too suggestive (like clothes covering exactly the nipples -apparently covering them makes an image family-frindly, even if you still basically have a bare boob - and private part down there), but somehow still family-frindly". As for words to replace "p*rn", I usually like to jokingly use "corn", especially since a website called CornHub exists (I did not misspell it, there really is a website about different kinds of corn in parody of the other website with similar sounding name).
Anyways UH. I mean you said it. There's sometimes correlation between the amount of suggestive stuff and how popular a character is, and sometimes there isn't. Others are favored for their appearance or ideas that get associated with them
What was UH? It is interesting though how some of the characters ended up becoming more popular in terms of inappropriate art. Like what made Sanae become the "doujin fam", same story with Reisen (even if for this one seems more obvious with the whole bunny girl thing, and the fact bunny girls have already been associated with inappropriate materials at least since the beginning of the Playboy magazine, so like 70 years ago).
Sometimes an artist becomes popular for drawing one character and others may follow suit
Probably the best example I know is Sazanami Mio, aka the guy who has always been drawing Youmu and is known for almost religiously drawing her. When I first found his art and Pixiv page, I used to nickname it "the cult of Youmu". But I was perfectly fine with it, as I like his/her woks, and Myon is a character I am fond of.
If you wanna get into the whole uh "why is this a thing" fuck dude idk.
Yeah, that is a good question. Without making a lot of analysis, I would just say "people are horny". I just think there is a difference between being horny and drawing smut of an adult, and a whole different story when you depict a child doing naughty stuff that basically counts as cp. But like you said, it's not always about sexual stuff, so I guess... idk. Still a little questionable unless your intention was that to make a character art study or anything akin.
Sorry for not responding earlier Count, there was more I wanted to discuss in the other threads.
No problem. Welcome back, and thank you for the contributions to other threads. Better later than never.
The observations you made for those with higher percentages are interesting. It seems that most of the 'mature appearing' characters, according to the fandom, get more of that fanart. As tenko said, the situations could also contribute to more fanart such as Aya being depicted as a pervert.
Yeah, that is quite the interesting part. Many of the characters on the top tend to be generally depicted as more mature, sometimes going into the "mommy trope". Again, avoiding the fairies and such (how did they even end up so high on the list? looking at you, Star, Luna and Sunny...), one other character I did notice but did not talk about, despite being one of my favorite, is Eiki, who scored a 7.51% on the list. At least from daily visits on Danbooru, one thing was to be learnt: if you see art of a mature Eiki, there's like 80-90% (depending on the day) for it to be smut. As if that is the only reason for people to not draw her as the little angry loli (even if there's smut of that too). Initially, I thought I saw Akyuu on the list, and was going to talk about that and say it makes sense she like the only 2hu for which we have a clear age, and therefore an adult, but then I noticed she was not listed in either of the images. However, Kosuzu scored impressively high, with over 12% of her content. That is literally every 1 in 10 Kosuzu pics.
Fusu:
I didn't know the person's name until now but their artwork was one of the first Touhou related ones I found on Pixiv. I thought the fantasy confessions were really cute and I have some of them saved too. I was wondering if they were taking a break when I also realized that they've been making R-18 content all this time. I found out earlier this year but I never knew since my settings were kept safe. Guess I won't be making a cute commission from them anymore, shame.
First time I encountered Fusu was through Reddit. It was towards the end of last year, when someone was daily posting translated Fusu art, and was gaining like 1-1.5K karma on a daily basis. After a while, people got mad, started a revolution, and made their own "counter-art" that was playing exactly on the opposite to what Fusu is expressing in his art. Following that, the translated art posts ceased.
Initially, I did save some of the confessions since I thought they are cute too, but then woke up to some sort of reality they might be "cringe" and simply addressed to those poor bastards with no gf (I am in no better shape, so yeah), therefore his art fitting perfectly with the whole topic of this thread. Just like you, I initially though his art does not go further than th confession art, but thanks to Danbooru, I learnt there's more to it. That's how I learnt of the "part 2" for each of these drawings, when everything following that confessions leads directly to naughty R-18 stuff.
That artwork of Mokou and Keine isn't too bad but it's an anime cliché I'm not a fan of. I often see this with the other characters too but it's mostly insulting.
On a second though, it does look a bit cliche. However, I still like it in some measure (more like drawing technique and stuff like that). Also can you please explain to me this anime trope? I have seen it many times, yet never took it as more than just "one of the girls has bigger boobs". Besides (possible) body shaming, I really wanna know why it is so insulting, especially knowing how commonly used the cliche is in media.