This and the couple of posts below kinda support my choice of adjective honestly, which I used because most of the negative comments about Ayase I read boiled down to emotional rants on her being 'mean and not a hero'. My comment was definitely a generalisation, hell i'd go as far as to say it was flippant, because it wasn't meant as a discussion for those who disagree but a note to the dev that some of us don't have issues with Ayase's character or story arc.
As for logic and reasons, I already provided the high level points on why I like how the character was written so far, and as I haven't had an internet debate in ages i'll elaborate on my position.
1- Ayase is not a hero. She's a vigilante. She all but tells you that herself. So any claim she didn't act as a 'hero' is pointless. She does sometimes act heroically though, eg. taking out bad guys the cops can't as a side thing at risk to her own person.
2- Her primary objective is finding her sister. Second to that is maintaining the ability to continue that search. And after that comes being a 'hero' or whatever. If you look from her perspective, then what she did is the only reasonable course of action. Let's go through it though:
3* The alley: Two parties over a naked unconscious girl blaming each other. Only reasonable option is disable all and sort it out after, which is what she did.
4* The initial discussion: First thing she does is apologize for attacking him (cause MC has been confirmed not guilty). Cool, yet she's now left with someone who knows her secret identity and spreading it, even if most people wouldn't believe it, might cause issues in her objectives (ie. she talks later in the game about her parents may restrict her freedom if they thought she was getting into trouble, so I took this to mean making her come home and not be out doing whatever and presumably limit monetary assets and other resources). She has zero reason to leave MCs trust to hold this secret to chance or 'asking nicely'. Hence the alley photo threat. This is a reasonable thing for her to do, coming from a vigilante mindset and given what she values most. Once secrecy is secured, she can then offer the carrot (MC's father) and work towards, well, working together.
5* The school stuff: You said "going as far to say that they should not interact at school so she can 'protect her image' Claiming her image is important after her obtuse behaviour with the picture is insanely stupid, that's like claiming to be a good driver after crashing your car." I mean, firstly this is factually wrong, she says to keep interactions to a minimum so things don't look suspicious. And secondly. that makes complete sense. She is idolized at school (many eyes on her whenever she's around) but doesn't interact with other students much, especially boys, so for maintaining a secret it would be foolish for her and MC to just start being familiar at school. Also, protecting her image has nothing to do with social climbing or power, but protecting her ability to look for her sister.
6* Later stuff: Later on she is clearly warming up to the MC and shows a fairly empathetic personality hiding under the badass vigilante persona, she just won't risk her goals for a stranger and as one can expect it takes time and MC actions over the story to build this trust (ie, not just saving her once in an alley, but consistent reveals of character through conversations, interactions with other NPCs and standing by her during the later fight). And Ayase starts opening up and reciprocating that trust/friendship + of course she never uses the blackmail/threat again for any purpose whatsoever (and apologizes more times for it) because as above, it was only to protect her objectives from someone she had no trust/relation with and not a power gaining thing.
7- You also said "Ayase has been consistently annoying, domineering and generally toxic, while the mc has consistently proven to be weak or mild-mannered to the point of getting walked all over."
This is essentially opinion, and one I don't agree with, obviously. I'd say its a perspective thing. A lot of time I see people in this forum complaining about 'beta' or 'spineless' or whatever synonym in some games, when what I and presumably others see is simply an MC that is reacting reasonably or with patience/caution because he sees not everything is as it seems at the surface.
8- I'll give you one concession though to round this out, Ayase definitely should have shown a bit more gratitude for being rescued. If not during the initial meeting, then later on, as I can't recall her ever really doing that. I view that more as a 'dev oversight' than anything else, as it doesn't fit with the character that's otherwise portrayed in the game.
Anyway, I'm guessing we aren't going to agree on this stuff, but all good. Cheers for reading my braindump!
(i numbered your points so you'll know to which one i'm about to try to answer)
1- Vigilantes ARE heroes, a villain knowing to be a villain would call himself a villain or complain that society doesn't understand that he is doing something evil but for the greater good. We also have anti-heroes, which are shady heroes basically, like Red Hood(in Batman) who actually do horrible things(like killing criminals), if you ask me Ayase is sort of between Hero and Anti-Hero, but more toward the anti-hero...but at this point it's irrelevant she thinks she is a good person, and i don't agree with it, i blame my poor choice of words for saying that she is supposed to be a hero and hero don't blackmail. That's on me, and i can only apologize.
(i skip point 2, because it's the introduction of your explanation about the situation XD)
3- That's fair...it's understandable, that's a misunderstanding, no problem with that, i'm not a vigilante, i wouldn't know how to react, but if i get some superpower, i'll make sure to have a gas-mask and a few grenades with sleeping-gas XD
4- MAYBE i'm too trusting but once i confirmed that a person is good and we're involved in a misunderstanding, i would just...avoided to talk about the picture completely or deleted it right away, because it could backfire so bad, as i explained a few times...Ultimately this "relationship"(yuck, make me nauseous to even say it in this situation) starts with the wrong foot but AYASE herself admits that she needs MC, that she wants HIS HELP...but does nothing to sugarcoat it...even when MC just decides to be cool with the risk of being framed, that's what i'm calling out: MC's reaction(for the most part) is lacking, he gets mad for 3 lines of dialogue and that's it. In the end, Ayase is admired by MC, i think it would have been better if she played the "nice part" considering MC's personality.
5- Honestly, i couldn't care less about this part, so moving on...
6- That would imply that MC can trust her, but he can't...he is still held hostage by a false accusation of rape(with a picture), trust is a two-way road and MC again is being blackmailed into help Ayase, how can he trusts that she won't use the picture to ruin his life? He can't but it's not acknowledged, but this connects with the 7°point because it's related to MC's personality...
7- It's not about MC being spineless, screw that! He fought 4-5 thugs and Ayase to help an unknown girl, that's pretty "spineful" in my agenda, the biggest issue is how half of the game(SO FAR) is flashback in a flashback(the game starts in medias res and triggers a flashback) and the other half is MC inner-monologuing about how great Ayase is in every possible way and then comparing everyone else to Ayase... which sounds more like the dev begging us to like Ayase by giving her tons of qualities, but ultimately he turned her into a Mary Sue, the only thing she isn't good at is being respectful of other people's houses, like demanding MC's bed when she is a guest, complaining that MC was spying on her when she walked out of the bathroom just naked, even though towels were there(she only needed clothes which MC was bringing) IN the bathroom. Again it's not MC being spineless but not standing up for himself, being walked over by pretty much everyone who isn't a male(MC's bestfriend deserves an award and a harem, that guy is my favourite character).
8- THAT'S WHAT WE'RE ALL TALKING ABOUT(in caps for emphasis), i think MC earned her trust by saving her a second time too, she could delete the picture because MC now is personally involved in the drama, Ayase still wears a mask, but MC doesn't, he is exposing his real identity no problem (actually the problems may come later, but that's another can of worms) Ayase could just delete the picture at the end of v0.1.5, also when you choose that you want nothing from her, she is glad, meaning that in her mind "her debt" with MC is paid by even doing nothing, that express how shallow she is, a good person who feels in debt would have insisted on repaying MC's help and kindness...
Bonus: We all forgot the picture, the tool for blackmailing that is sus but not compromising really like MC is dressed a bit on his knees(like halfway through a squat) in front of a naked girl in the missionary position... HOW IS THAT COMPROMISING?! It is for the girl, because that's public indecency... MC is all dressed, no genitals in sight, not even touching her. Not to mention how a hidden PHOTOcamera took the picture, does the necklace have a special button to take a picture, or it's a hidden VIDEOcamera that records everything and Ayase took a frame of whatever she recorded? <- this is insanely nitpicky but i thought to share it XD