Heiwajima Shizuo does not get rage blackouts.
Instead, he is perfectly aware of his surroundings and actions at all times. The world doesn't blur or fade away. He doesn't lose his sense of self or time or reason. No, Shizuo always knows exactly what he is doing.
He knows, but he doesn't care.
What happens when Heiwajima Shizuo gets angry is a several-step process, but it always starts like this: someone irritates him. He doesn't have to be furious – just irritated. One sure-fire way to do this is to lie about or otherwise misrepresent love. Another way is to talk about Hanejima Yuuhei like you know him or possess him. A third is to gang up on someone much weaker, or otherwise go after the helpless. There are myriad other reasons Shizuo becomes irritated, but those are the most frequent causes.
From irritation, it's a simple step to frustration: if the behaviour continues for any significant length of time. Orihara Izaya is the only person truly capable of throwing Shizuo into an immediate rage; short of suddenly trying to kill someone, it's really hard for other people to get Shizuo immediately angry. Of course, since most people don't notice his warning signs, his tempers seem very sudden to them.
Warning signs include heavy smoking, clenching fists, gritted teeth, glaring, and deep breaths. Sometimes there will be a verbal warning from the man himself, but generally by the time Shizuo talks it's already too late to take anything back. (That also annoys him, when people will suddenly try to reform their behaviors around him out of fear.)
Of course, his reputation creates such a skewed impression of him in the first place, not to mention that he smokes frequently when he isn't angry as well, and he generally wears sunglasses that make it harder to read his expression. So most people don't ever pick up on Shizuo's warning signals; instead the vast majority make it a policy to just avoid him altogether to be on the safe side.
But if someone fails to back away swiftly enough, or if Shizuo has already become irritated and some foolish delinquent or other continues the behaviour that got on his nerves in the first place… then Shizuo will cross a line in his mind.
It's the limit for most people, the marker beyond which his enormous strength lies. On rare occasions, other people can also cross that line – the classic example of a mother lifting a car off of her children comes to mind – but for Shizuo, it's an easy step that requires no extra exertion and is shown only through dropping his cigarette and crushing it under a foot.
Beyond that line, the world shifts around him. He is completely and utterly aware of everything, he knows what he is doing, he even plans his attacks to the extent he ever plans anything.
Because when Shizuo is in such a rage, his morals slip away. His reasons for attacking make sense to him. A stalker, claiming love; a delinquent, attacking a helpless woman; Izaya, showing his face in Shizuo's city – they are all asking to be attacked.
The world around him shifts. He does not see people, vending machines, stop signs, or even trees – everything is a potential weapon, everything a possible way to show the person in front of him what he deserves.
"Who do you think you are?" Shizuo often asks his victims. "Do you think you're God? Huh?" Or: "You just attacked me. That means you wanted to kill me. So that means if I kill you, it's okay, right?"
He's not just saying these things. He really means them. His logic warps and, rather than being unable to stop himself, when in a rage Shizuo simply loses all inclination to do so. That's at least part of the reason why, when he calms down, Shizuo feels so ashamed of himself. Every time he comes down from a rage, however brief or destructive, Shizuo feels as though he has lost yet another battle in a war, and the casualties are everyone around him just as much as his own emotions.
And, in a sense, that's why Heiwajima Shizuo is so dangerous – not because of his strength, but because no matter how much he cares both before and after the fact, during his violent rampages, he is capable of just about anything.
He won't attack those he views as innocent, but then – that doesn't mean he will protect them, either. Sometimes, he might, through sheer accident or his own fury cooling just in time. But just as frequently, Shizuo will fail to even notice or care about the damage he causes property or people. It's been that way ever since his youth, even though at least once his lack of caring for his surroundings has caused him to lose something very important to him.
Only once in his life has Shizuo won a battle in his never-ending war with his own mind (because it is his mind he fights against; however monstrous his strength, it is at least understood and controlled when he's calm; he never breaks things accidentally) and that was when the Slashers, the many children of the demon-sword Saika attacked him.
But, at that time Shizuo wasn't angry. He was frustrated, perhaps, but he didn't have any one person to be angry at – and Shizuo never loses it without a focus for his fury. So, at that time Shizuo was still in control of his mind and though he was fighting so very many people, they were all innocent as far as he was concerned, and in a sense it was almost easy not to seriously harm them. It wasn't really easy, of course; no matter how superb his control might be, the situation itself, with them refusing to stay down due to their possession, made not destroying any lives a conscious effort.
The effects of that one battle won are both great and small; Shizuo has gained a sort of mental peace with his strength, at least, and to some extent his temper as well. The victorious feeling of knowing he didn't kill anyone even with literally hundreds of people surrounding him and trying to (as good as) kill him; it makes it easier for Shizuo to focus on what he really wants rather than the irritation bubbling up inside him. And since Shizuo only wants to live in peace, remembering his desire to do so makes it easier for him to calm himself down – a huge victory.
At the same time though, the victory is meaningless and has made no difference whatsoever, because he may be able to stop the process more frequently now, but only the beginning stages. Shizuo still has no control over his mind when that switch is flipped and his rage takes over. He still abruptly, if briefly, changes his whole philosophy and, focused on ending a single thing, would gladly destroy the whole world without minding in the slightest.
In a sense, it's not his fault. The switch, though rarely flipped for any other human, has always had the same effect. Any human experiencing that huge surge of strength does so with a single-minded kind of determination that leaves no room for concern of anything outside its focal point. If the mother lifting the car off her child had to tip it over on top of someone else in order to save her child's life, she would probably do just that and not think twice about it.
But for Shizuo, his focal point is generally not saving people – thanks to his temper, it's destroying them. And since his switch is so easily flipped, the fact that he reacts the same as anyone else would afterwards makes no difference. He holds himself to an impossibly unfair higher standard and he should, for all he constantly fails to meet it.
And so, no matter how he tries, until Shizuo's mind follows the lead of his body and accomplishes the impossible, he will never gain peace. Until he becomes capable of changing that hyper-focus into a more general determination, until he blunts that essential knife's edge hidden inside every human, Shizuo will never win his war.
Unfortunately, the world around him will pay the price. Because, yes, Shizuo is one hundred percent aware of his every action, and when in control of himself, he'd give anything to undo what he's done.
But so long as he doesn't care, he'll do it over again a thousand times, and laugh all the while.
I'm considering making this into a several-chapter work, based on analyzing several different key emotions in regards to Heiwajima Shizuo. I've got tentative ideas on love and pain already. If there's enough interest, I'll continue and aim to make this a sort of 'five truths' type fic. If not, I'm content leaving it at this.
...Seriously, words cannot express how much I love Shizuo. I've got to try, though, hence the creation of things like this.