I think an important thing to note about the fan reaction is that it isn't actually a "we didn't see this coming" type of shock, it's more of a "we didn't think they would actually do this" kind of shock. The possibility of Kaito and Shinichi being related has been considered a crack theory for a really long time, and when the staff revealed that there wouldn't be any pre-release for the movie because of a certain "spoiler", many were already making jokes about the said reveal being kaishin actually being related (which ended up being correct). But it was simply treated as such: a crack theory. Basically something that the official source hasn't disproved but also seems too "out there" to be true. Hence the surprise when it actually did turn out being true.

Also the episode with Yuusaku and Toichi didn't actually reveal anything about familial relations — it's basically just a nudge towards that direction. A hint, but not a confirmation. In the episode/chapter, Toichi says "I am your little brother" to Shinichi, and the explanation officially given with regards to this line is that it's about Shinichi and KID. Toichi speaks this line as KID, who is Shinichi's little brother because Yuusaku is the one to give him his name, essentially giving birth to "Kaitou KID". This is the official deduction given and there are no other hints that tell us that there was any more importance to that line besides it being part of the riddle. It was never brought up again after that.

Besides, the anime staff wouldn't have made a big deal of the reveal of Toichi and Yusaku being brothers (by cancelling the pre-release so that people won't spoil it, and by putting the said reveal at the post-credits for the most impact) if this was already confirmed beforehand. What would be the point of putting that much importance to something that was confirmed 600 episodes ago? The answer: there was never a confirmation to begin with. It's only in movie 27.

A lot of people also point out Kaito and Shinichi's similarity being the most obvious hint too, Kaito isn't really the only character acknowledged by the characters themselves to look like Shinichi. Okita is there, and Heiji literally tries to gaslight the media when Shinichi appeared during the school trip by telling them that it's actually Okita. So if people thought Kaito and Shinichi are related simply because of appearances, then Okita would probably be related to them too. (Who knows, maybe we get another reveal in the future, heh). For the longest time too, many assumed the jokes poking fun at their similarities in appearance are a callback to the fact that Aoyama recycled his character designs from Magic Kaito for Detective Conan, just with minor tweaks (Kaito - Shinichi, Aoko - Ran, Ginzo - Kogoro).

On top of all of that, I think a lot of people are just bummed out that such a major reveal was done in a movie that isn't part of the canon, as opposed to being revealed in the main series. And the fact that it's been 30 years too long.

That is an honor omg. Seems like a good time for me to say I actually curate my public bookmarks to contain my fic recommendations? I curate it for the sole purpose of giving recommendations to people who like to read the same things I do, but I fear there isn't a lot of kaishin in it since I actually haven't thoroughly scoured the tag yet (I am a chronic "open the tab to read later and then will never read it" kind of person... sorry anon). If you're stillll interested in my recommendations though.... here's my public bookmarks. 14/19 is DCMK so it shouldn't be hard to scour. I keep it at a low number so it's not overwhelming. https://archiveofourown.org/users/pepperworks/bookmarks

I don't really do DNIs. I function more on a case-by-case basis where I judge personally if someone's behavior or language doesn't sit right with me and if I really don't want them to interact with me, I block immediately. I'm more likely to block someone over continuous aggressive language or encouraging negative behavior than I am over a fandom opinion I don't agree with because I also like reading different opinions. Also, sometimes I like to piss off people I disagree with (the usual DNI criteria peeps mostly) so I don't block them... they'll just have to do it to me sorry not sorry lol.

Thank you for asking! Appreciate the thought.

Honestly I think I talk a lot about my favorite ones lol. Like, Conan's Kaito KID radar? Technically it's canon that Conan can sense when Kid is around, but everything else about it is headcanon territory, like how it works and stuff. There's also Akako's magic not working on Kaito because he's gay or trans (either he's just not attracted to girls OR Kaito's mtf and hasn't realized it yet but the magic immediately clocked Kaito as not a man hence getting exempted from it. Can't also help that Kaito really enjoys dressing up as cute girls. Just give it a few years or something).

Also that Kogoro is a competent detective but Conan solving the cases for him has made him somewhat lazy. I absolutely miss the days when Kogoro was suspicious of Conan and think it's a shame we don't get that anymore, so in my head I kind of just think that Kogoro is competent but just slower at piecing things together, so we don't actually get to see him shine much (and also why he gets very competent in cases that are personal to him, because in those cases he has a personal sense of urgency). He probably sees the whole Sleeping Kogoro thing as convenient for him and that's why he hasn't been as suspicious of Conan as before and that convenience makes him not really care into looking into it. Like "it's helping me, so why even bother".

Someone has definitely suggested to him that it's probably a medical condition AT LEAST ONCE, and he just laughs it off. He gets himself checked. They don't think he has a medical condition. And he's back to ignoring the issue again since the Sleeping Kogoro brings food to the table.

An obvious one would be KID as a dove... but also, a pigeon. The only real difference between a dove and a pigeon is linguistic, while many associate dove as a gentle white bird that symbolizes peace, many think of pigeons as pests that shit all over the place. Just the same kind of bird but different names come with different associations, like KID the gentleman thief and Kuroba Kaito the regular highschooler who loves to make pranks.

As for Shinichi I associate him with a raven. For one, it's their association with omens and bad things happening, which Shinichi himself is prone to as a crime-magnet. And Ravens are able to mimic sounds of other birds, which is something Shinichi does (even if it's with help of an equipment). Also probably the association with Edgar Allan Poe.

I'm really just going off of what I gathered about these birds on the internet and I'm not at all an expert in any of them (just a disclaimer in case someone is and they see this and they think I'm saying something wrong lol) but I closely associate them with birds... but also cats. Though my explanations for cats is more surface level, such as how they act at times or how they are treated by other characters.

Oh trust me, limiting myself is THE way to go lol. I keep mentioning the fact that my account was actually a private acount before the kaishin incident because I want people to know that I am actually a very private person, and that I get uncomfortable very easily. When I was a private account and my followers were manageable and under 100, I would literally check which accounts I am not close with (aka those who just never interacted with me, or who i was no longer in interacting terms with) and remove them as a follower. That was how I maintained my comfort level and how I ran my account for four years. That meant I knew almost every single person following me and they knew me as well, so I can freely say things without fear of, say, someone responding weirdly, things I say being taken out of context, my words not landing in a way i intended etc. Of course I can't do that now seeing as how I have 1.4k people around now after Movie 27, but just because I am more public now doesn't really mean I am okay with people having all kinds of access to me. I really wasn't even expecting to be a public dcmk account at all, because I was perfectly content with tweeting privately even without an audience as long as I got to keep my peaceful corner. I'm still very introverted and very private and nothing has changed about that even if I'm public and post art and make jokes often. I like to be the one to judge first if I'm okay with being mutuals with a person, and really the only way I can judge is if people keep interacting with me. Like, if you keep replying to my tweets or sometimes even just liking. I usually remember every person who consistently interacts with me even if it's just liking anyway, so I do encourage that. I like interacting and making friends. It just takes a while for me to be trusting, especially on the internet. It doesn't mean I completely close myself to new people.

TL;DR yesss, it is perfectly fine to interact with me on twitter! I just take a long time opening up.

Also this was probably a longer answer than you expected lol. I saw the opportunity to talk about my own boundaries and comfort level and took it. I think it's stuff people should know about me anyway, especially if people wanna be friends :D