
Well, in real life Natsuo couldn't be a bad person, because he rescues stray cats. That's just the way the world works - if you're kind to animals and take in strays, you are a good person at heart. That's it, I have faith in him. He may have unrequited love for Kousuke but he's still a good guy. He just needs a love story of his own. It's not his fault he's the "complication" plot device character!

I love this mangaka so much. It's so rare that cheating in yaoi is treated as anything more than a simple/cheap plot device. I actually find it brilliant that the story is gut-wrenching and unsettling, it can sort of get our heads on straight again and remind us that cheating can actually break hearts, damage people and ruin lives - hopefully not forever in this case though.
I don't think Arata ever would have even imagined himself being violent towards Na-chan, if he hadn't been wounded and betrayed by Na-chan cheating. And now from both sides (Na-chan hurt Arata emotionally, Arata hurt Na-chan physically) they have to deal with the fact that their relationship, as it was, is broken forever.
I don't even have an opinion on what I want to happen, which is unusual! I just want to see where the story and characters go, because it's so damn interesting.

I love his personality!! This is a "bully" character done exactly right (for my taste). He enjoys teasing and watching his kouhai's reactions, but he always tells him the truth immediately, so he doesn't continue to feel bad. Most "bully" characters are borderline-emotionally-abusive arseholes who enjoy watching their partner feeling sad, insecure or inferior for ages. Senpai is perfect!

This story is thought-provoking and unsettling, and in no way a romance. Look not here for a love story. The top tag is "psychological" and that is good solid tagging. (This is going to be spoilery.)
I'm going to say it straight - Hikaru, as a teenager, does not have a "frozen heart" or anything so beautiful-sounding. He is a psychopath from the very beginning. And I use the term psychopath in the clinical sense. Psychopaths exhibit shallow affect, manipulativeness, lack of empathy, criminal versatility (for example, a willingness to commit rape, abuse and blackmail), impulsiveness, poor behaviour controls, lack of remorse... he's all over the psychopathy checklist. The only thing that makes me consider sociopathy instead is that he does feel such disgust towards people he doesn't like, especially girls/women, presumably stemming from social surroundings and events while young. He also gets upset when things don't go the way he wants them to. Even so, psychopathy is a spectrum disorder, and it can be triggered by childhood environmental and social factors, anyway.
The masterful thing is, we're supposed to know this about Hikaru, because we're shown more than enough in his actions to reveal it. Hikaru's emotionless, calculating, dead-eyed look when he's manipulating Haruki is always chilling: http://www.mangago.zone/read-manga/kokoro_o_korosu_houhou/mf/7416b322c0721ad006c92fde0e6d41a5_chapter-1/pg-22/ and elsewhere.
And it's awful that Haruki even understands it as it's happening: http://www.mangago.zone/read-manga/kokoro_o_korosu_houhou/mf/7416b322c0721ad006c92fde0e6d41a5_chapter-1/pg-23/.
As well as this, to some extent we're also shown and told the way Hikaru experiences the world, from his perspective. I don't think it's to make the readers recognise him as the "official" love interest, like in so many yaoi manga - it's to let us understand that he truly is fucked up, it's not just Haruki's interpretation.
Psychopath Hikaru develops an intense fixation towards his kind older step-brother Haruki (who would have been perfectly fine as a kind, gentle person, if he'd never met Hikaru) - and we see the result. He breaks him. And breaks him. And breaks him. He thinks this is love, but there's no sense of empathy or interest in Haruki as a human being with an identity and feelings at all.
Finally Haruki is so shattered that the possibility of being with the one he actually likes from early on, Hanabusa-senpai, is ruined. And in the end he feels he can only feasibly be connected with his abuser, because he misrecognises Hikaru's mental disorder as some sort of kindred brokenness. Hikaru is broken because of his brain chemistry/genetics, and sometimes by the consequences of his own actions (although it still feels like he doesn't properly feel or understand this). Haruki is broken because it was done to him, by Hikaru.
Like I said: this is not a love story. Especially if they end up together. Actually, that would deserve a tragedy tag in and of itself. (But none of this means it's not a good manga.)

I really don't mind Zono sleeping with other people/person. They're not in a relationship, it's purely physical for both of them at this stage. Cheating is bad of course, but if there's not a mutually agreed-upon monogamous relationship, people are free and entitled to sleep with whomever they want. Even Zono saying "I like you" doesn't change that, people can "like" someone or more than one someone in different ways. And Fumi doesn't "like" Zono at all (yet) but enjoys having sex with him, so fair's fair! By the way, in my philosophy this is fine whether it's women, men, seme, uke, seke, whatever.
I agree with what someone said about it being an unrealistic start to their physical relationship (seriously, whut?) but aside from that this is a type of storyline I like - purely sex (enjoyed by both parties), developing into feelings.

To a point, once you start to talk for a while there is no reason to excuse them sleeping with others, there is an unspoken promise there. The possibility that you'll start dating. I'd even argue that if you're at the point that you want to date someone you wont WANT to sleep with others. I feel like that's just how both social interaction and the emotional dating process work. You're free to mess around until you go out of your way to talk a lot with an individual because then they get expectations. He was spending a lot of time and having sex with Fumi, but this case might be a special one because Fumi wasn't interested at first, it was just good sex.

Personally, I don't agree that talking a lot is enough to assume a relationship (even having sex isn't necessarily enough). I can understand some people having expectations from that and potentially getting hurt, which is sad - and if that happens, of course there's no reason for those people to excuse it or put up with it. But talking or flirting a lot still isn't enough to imply any kind of promise. As soon as terms like "dating," "relationship," "boyfriend/girlfriend," partner," "lover" etc. are used I do absolutely think that carries a reasonable expectation of exclusivity. But not until then.
As you say, I think this case is special anyway, since Fumi didn't even want to be in a relationship with Zono - until now? - and they haven't even discussed that. I'm expecting the plot to be the two of them developing real/deeper feelings for each other. And I am hoping it's not going to be the cliche "uke gets hurt (and jealous), and only then realises he loves the seme" scenario. But we'll see, I guess. They're interesting and a bit unconventional together so I'm looking forward to it, I hope it's good.

At this point I really do hope Seno is pretending... so he'll see for certain what a piece of shit Natsuka is and leave him. Natsuka is so selfish, and honestly doesn't seem to care about others. He even sees Hakushima (apparently the one he loves) the way he wants to and didn't want to face reality, back before the accident.

That's what I thought - and even though I hate that he's being hurt, if it makes him leave Natsuka I think he'll be better off in the long run. I feel the same way I do when one of my friends is upset about their shitty partner and I'm being sympathetic but internally I'm chanting "Leeeeave them, leeeeave them"

...Am I just hurting myself by hoping that he's imagining this? Although it would still be scary for him since his delusions are ultra-realistic, I hope Kureshima's just doing the erotic voice-over like last time...
I've been around the yaoi block long enough to have completely lost any innocence or naivete about the genre, but just once I want to think better things of him, is that so wrong? ╥﹏╥

I feel like so far this manga ALMOST gets to the point of exploring a really important and interesting subject that's rarely done (or at least rarely done well) in BL. Kiyou doesn't want to be gay, even though he's perfectly aware that he pretty much is. He wants so badly to be 'normal.' He's scared of being judged and singled out and rejected by those around him. I think it's an amazing moment when he thinks "If I accept him these will definitely be requited feelings," but he's scared and reluctant and unwilling and wants to run away, and he knows it. These are realistic feelings for some people, in situations like this.
I feel that Tsurugi's feelings and actions, and his frustration, are understandable in this sort of scenario too... But that gets kinda lost when he goes all psychopath crazy-eyes, clutching a tie and saying "I'll make it so you can't get away." Realism took a bit of a nose-dive for me there. If only the style wasn't BOOM! SUDDEN YANDERE! but instead was more upset, frustrated guy saying "Why won't you face me honestly" or something. Just a slightly different, less psycho vibe would have been great for me! And in my opinion, it wouldn't have taken anything away from what happened afterwards, just given Tsurugi a less unhinged feel right then (I don't even think he seems like a yandere in the bathroom stall... yet, I guess, next chapter may prove me wrong). I'm not a fan of yanderes. But hey, it's not my manga.
I know the way DG is thinking might be normal for some people... but I find it naive and annoying that he thinks Jiwon's personality would completely change if they started dating. Jiwon's been straightforward about his attitude to relationships and dating from the start, and that wouldn't be likely to change easily even if (when) he develops feelings for someone. DG's not seeing the real person, he's seeing what he wants to see for a "boyfriend." He's acting like a stereotypical shoujo girl (who happens to like watching porn). I wish he'd kept being a sweet-but-refreshingly-not-naive-to-the-point-of-stupidity guy about it.
Just wanted to add - Totally Captivated is a great example of what I'm talking about. Mookyul's PERSONALITY never changes. He learns to change his behaviour - as he should - and it's a hard lesson, because he really does love Ewon. But he is who he is, and Ewon knows him and loves him. Much more realistic and (for me) satisfying.