Isn't that the point? Chiaki was extremely shocked at what was going on, it even took him time to realize Ayumi was being serious. This same feeling was put within myself BECAUSE of the suddenness. People keep making it out to be a fault, but not all mentally unstable people are super obvious about it. Ayumi isn't a psychopath, he is more of a sociopath, you can tell from the way he comes across normal but from his interactions with Chiaki you can see that he's pretty unfeeling as he has no friends, likes to Chiaki's different emotions and likes to take things from people all the while not realizing that what he's doing is wrong. The story has been really attention grabbing and i think the sudden 180 is actually a really good presentation of Ayumi's personality. Also, the foreshadowing was there, it just wasn't as obvious as a dark background around a pan-in on a gaunt face. The foreshadowing was the multiple "questionable" moments were Chiaki pointed out that Ayumi was "weird" , we just thought nothing of it because the story didn't allow any focus on it, it's been all about Chiaki.
To be fair, this whole change they made is confusing. I personally don't think it is supported. Yes, it showed the seme wasn't innocent but with so much angst, you'd expect a big fight, him getting into outside trouble because he is troubled. Yes, chiaki was indecisive and couldn't make a jump to move on but I fully expected him to have an epiphany and lead to change. There's a feel in yaoi where you sense danger in a character, an aurora or intent felt, but ayumu didn't have it. The previous chapters had a " there's gonna be a lot of miscommunication" feeling.
I think the lack of that "feeling" you're describing is intentional. What you're describing is a psychopath, they're both inwardly and outwardly disturbing, however a sociopath is able to fit in with society. I think you're wanting clear cut signs because in most cases, in my personal experience, yaoi with all the messed up shit involve psychopaths, not sociopaths. You're used to them acting a certain way. They approached the signs of a sociopath in a very realistic way in this, imo. The signs aren't the type to jump out and with the story being focused on Chiaki you don't really allow time for yourself to think about Ayumi when he does weird shit. The goldfish thing for example, it is made known that he is detatched from emotion here, he wants that fish and even to this day is irritated that he can't have it. In the flashback he saw how happy the kid was with his goldfish, but didn't care and was just irritated, even as an adult. Even before the goldfish thing we find out that Ayumi doesn't actually consider anyone as a "friend", even the people he goes to school with and laughs and jokes with everyday. He is fitting the role well, but has no connection. A "friend" with no feelings towards any of them. When he chains Chiaki up, it is normal to him, "when you have something you like you hold onto it, right"? He doesn't realize that what he's doing is wrong. He is an emotionally detatched mentally unstable man able to outwardly appear normal, a sociopath and the clues to that look pretty obvious in hindsight. I don't think you were supposed to notice the clues as you read, i didn't, but you WERE supposed to notice them after the big reveal, like "oh, this is what those events were making me feel off about". You were supposed to see the clues and continue on with a slight, ignorable amount of unease because that is how a sociopath is, they pass as normal and any "weird" is just in passing.
Really? I must have misunderstood what you were saying. I was responding to these lines: 1. "There's a feel in yaoi where you sense danger in a character... Ayumi didn't have it", to this i responded by saying "i think the "feeling" you were expecting that isn't there for you is because the predominant villain type is 'psychopath' rather than 'sociopath', the clues wouldn't be as obvious on a sociopath as they blend in". And 2. "to be fair, this whole change they made is confusing. I personally don't think it is... Because he is troubled", to this i responded with "a sociopath wouldn't be getting into fights and making a scene, what you're describing is a psychopath, they are inwardly AND outwardly unstable. Sociopaths are inwardly unstable and outwardly normal". I hope that condensing of my point has made it easier to understand.
Yeah, I'm not sure about this manga anymore. Chiaki was a bit annoying but then the seme jumped to kidnapping in one page and ignores everything he says. Which is fine if it is supported by the plot, settings, and characters but it's not and there was no transition. No foreshadowing either.