@CinnamonRoll ayaaa, i cant express just how glad i am to know you like my characters so much ;-; <3 it means so much to me.
(i updated that name like 3 days ago, so today's the day xd but ty ^^ <3)
Okay so, to be fair, Mahiru is the one character i have most trouble with, from all points of view. I cant stress enough how long it took me to even find something that would let her get out of the "evil for the sake of evil" category even just for a little bit. Even her backstory is not 100% original, its something i found somewhere else and applied it to her hoping it would create a starting point for her to develop something that would fit better. She's the main villain, and one i intend to make audiences care for, but also fear at the same time. If you've read Heaven's Official Blessing, that's the kind of villain im going for - but me and making villains dont really seem to get along :"))
Her loyalty thing was kinda meant to go something like "okay, i dont mind serving this dude as long as he doesnt get involved in something that goes directly against my plans" which is usually the case, because no human king would be able to interfere with her quest (we're talking divine power here). Besides that, she kinda twisted some bolts and screws here and there to focus most of the king's power into her own hand to ensure she would not have issues in the future - the king is more of a puppet at this point. Also, the 'bad' things are kept underground where no one can find them unless actively looking for them - just searching would be hard enough given shes erased most of it, but if one does happen to find any leads, shes swift enough to eliminate any potential threat of exposing her, and she will find ways to cover it up seamlessly.
Im thinking of making her calm down after taking her revenge, so she's cool with working under a monarch cuz it offers her the power to do her things without issue. Now she just needs to make sure no information on her slips out.
Again, she wasnt in a very good place mentally when she did the things she did, so its a case of "shit, i revealed the most evil side of me to everyone, they're gonna hate me now - gotta fix this". I've encountered cases in real life of people who slaughtered everyone close to them out of fear they would be hated for not being the one everyone thought they were. Here's some cases like this. (Thomas Bartlett Whitaker and Jean Claude Romand are very close to what i had in mind). Basically, Mahiru could not live with the idea of people knowing what she'd done, so she just wiped everything and started over - not like she had that many friends left anyway. Of course, not having anyone to rely on anymore did affect her, but she just surrounded herself with new people.
As for revenge, her main target were those who wronged her. Deities in this world arent exactly gods, more like powerful spiritual officials that take care of various stuff and can be replaced. The ones with a bigger role are the Great Spirits, who are like the top 5 most powerful of all spirits (Mahiru once held this title as well but lost it after going berserk and maybe even killing one of her fellow colleagues. Current Great Spirits would include Hanami and the Oracle, who got her spot for being the walking information dispenser she is).
Currently, Morphidae are the only ones still able to call her out but their numbers have been thinned out enough that shes confident enough that she can keep them under control. I did mention she found a way to turn those guys into creatures that serve her, thats why periodically she snatches a few to see what new version of her demon weapons she could make (so far Rin is the best version) but the rate at which she's picking them is often enough for their numbers to decrease steadily, given their birth rate can't keep up with the losses - and you know experimenting is all about trial and error, so you realize she messed up plenty of times before she got things right. She officially carried it too far when she went for the Morphidae prince, fearing he might be capable of taking her on because of his mixed heritage (he has the potential to reach the same level as Hanami and kick her ass for good).
As for the Great Spirits, i havent really thought why they dont just smite her from where they stand - maybe because she is technically on the same level as them and fighting her would make a huge mess. They're not ok with her actions, no, but they dont directly interfere with her either (cant say if its because rules, not wanting to get mixed up in the mess or just not knowing what shes doing because she's so very secretive and careful with her planning.) So far, Hanami is the only one who is taking some form of action against her, through influencing events so her damage is minimized, but im telling you, if she ever pushes him over the limit (which is pretty far giving he's a Morphidae and they have a crap ton of patience with shit like this) he will not hesitate to show up and fight her then and there.
Hoooo boi, this got long :"D Mahiru is one character i would really like to talk about, given she's a villain and i would like to develop her to the extent she feels real and valid - most of the story revolves around her, so i consider her very important and try to give her as much solidity as possible. Any ideas are welcome, really <3 The notes were really helpful, really gave me a few questions to wonder about regarding her, thank you so much yvy <3 ^^ perhaps you might be able to help me develop her further? only if you want :"D