Why do you think hori decided to make decay one part of overhaul? I know many fans believe its so he can awaken the reconstruct part later but that sounds too contrived
hmmm, my take is... it's to make the world more boring, making AFO a super dick who's responsible for everything wrong in the world, and so relieve a burden from the Heroes.
It is my belief that people are too caught up in the Overhaul part (while also too dismissive of Overhaul the guy), and part of that is the need for copium for Shigaraki to come back and save his League/redeem himself. They need a miracle for the League to survive, and they need an excuse for Shigaraki to not be treated badly by the Heroes afterwards. If Shigaraki has 'Overhaul' quirk, and proves himself by having the ability to 'heal', then Shigaraki can justify his existence to the Heroes as useful/less lethal/benevolent-due-to-healing-power. I know that's not what's intended, but that's what it comes off as. Shigaraki with 'Decay' gets killed by a Hero; but Shigaraki who comes back (especially as Tenko) with a different quirk can stay? It's a bad look, even if coincidental.
(But who knows! Maybe he will do exactly that. We're at Horikoshi's mercy.)
I think the derived-from-Overhaul thing is just to make AFO a super asshole who went out of his way to make A Very Dangerous And Scary Quirk, one that will guarantee ostracizing status for Tenko because society already discriminates against 'villainous' quirks - and by doing so, actually gives Hero an easy out of doing something about their quirk society.
Decay - a five-finger automatic touch disintegration quirk - is a highly, easily destructive and lethal power. If it's naturally existing, if a five-year-old can randomly awaken this ability, it spells out trouble for the world. How would parents respond to their child having such a quirk? How to treat this child with the full love and respect they deserve - because all children deserve full love and respect! - without alienating and hurting them? How would one raise this child to be mindful and careful and responsible, without also overburdening them or making them feel like they're a dangerous monster?
Is the solution to make Shigaraki/Tenko wear gloves? That seems simple at first, what if Shigaraki/Tenko doesn't want to? What if gloves are annoying and gives him rashes from wearing them all the time or it interferes with his hygiene? What if he simply wants his hands free? But when his gloves are off, people get antsy and nervous around him, worrying about that 'what if'? How do you balance personal autonomy and other people's safety? How do you balance "what is convenient for other people" with "what is right for me?"
Decay is a really interesting quirk to exist in a world where quirks can be anything and in a story that asks what it means to live in a superpowered society. We've seen that HeroAcaLand is not very kind to people with quirks that gives them trouble fitting in with a norm. Quirks that violate taboos like Toga's; quirks that give people 'scary' or 'gross' appearances like heteromorphic quirks ; quirks that are seen as 'villainous' - the people holding these quirks (which is their innate ability, a natural part of themselves as much as their eye color and limbs!) get mistreated because society lets their prejudices and preconceived ideas take over and taint their treatment of such individuals. This is a problem in the world of bnha, but it's rarely ever touched upon besides a general lesson of basically "tough luck, mind yourself and suck it up until things get better".
People have pointed out that Toga's quirks and heteromorph quirks has got this covered, but Decay is unique in its seemingly mutation manifestation and its extreme aspects. It's automatic except for a few conditions; it's immediately lethal. It would be been so good to see how Heroes handle that.
Deku stops Decay only because he's in the dreamscape and can just imagine himself not getting disintegrated. How convenient! If it had taken place in real life, how would he have dealt with Decay in a way that wouldn't have scared Tenko off yet also protected Deku's and the Shimura's safety? Would Deku tie the five-year-old up with black whip? Would Deku hold (and break) his wrists like he did with Shigaraki in reality? Would Deku have to evacuated the Shimuras, leaving poor Tenko to watch a Hero save people *from him*, and then remain alone for however many agonizing minutes? Would Deku be forced to stay far away and yell encouragements while waiting for backup, for the right Hero with the right quirk to come (essentially mimicking what Heroes made Bakugou go through in the first chapter?) It's good for Deku to want to rush in and save people without a thought, but what to do in situations where he cannot get lucky and cannot do that without dying? When the 'trouble' he's facing is the very victim themself?
If Decay was naturally occurring, these are questions Heroes must deal with, these are incidents and emergencies Heroes must be ready to face. Hell, these are things parents must be prepared for and have drills and plans set aside if it ends up being their child with such a quirk. (Like, it's awful that Kotarou's instinct when faced with an unexpected and scary quirk being 'whack your son with garden shears' instead of 'calmly assess the situation, remember what the parenting book said about quirk manifestation, and comfort your child'??? And no, I will not take 'Kotarou's just a dick, nvm him' as an answer. It's not about him specifically anymore, I'm talking about what a parent should have done in this situation in general. Because Nao just died! She loved her son and tried to go to him and died!) These are questions society must find solutions for. Otherwise, tragedies will happen; fear sets in; people don't get saved.
BUT as it turns out, Decay is not naturally occurring. AFO created a quirk like this for the ultimate tragedy, meaning tragedies like this don't actually happen. At worst we get Eri's case - her dad disappears but without too much mess, and there's a wind-up time until the next incident, and we even get a visual warning in her horn growth. And thankfully we have Aizawa, an adult, already a licensed Hero, there to keep her in check. And if tragedies like this don't actually happen, that is not a thing Heroes have to lose sleep over. Quirk accident resulting in multiple casualties? A quirk that kills so easily? A quirk that appears in a suffering child and interacts with their background in the worst way? A quirk that would've subjected the holder to a hard and isolating life (largely due to other people's attitudes towards it!) and if Deku's a Hero who wants to save people, what will he do?
Well. Not a thing Deku has to think about. Wasn't real. What a relief.
