Quite literally plot armor made manifest to its logical conclusion. Your entire life is a plot whether you realize it or not, and until you finish that plot, it's impossible for something to force you to deviate - until an unpredictable romantic variable enters the fray, and then the plot armor...
Attempts at redemption require a lot more than just half-hearted apologies, and he really needs to know how low he went for someone that's supposed to become a future Emperor. Just because Melissa was full of crap as her old self doesn't mean what he did would be justified in anything other than...
Literally what can she do in any of this? Shout about the High Priest that would be protected by any claims she makes? She'd be disqualified for blasphemy more likely than not. What can the Knights do if the Priest doesn't actually directly hurt anyone? They have no proof that she intentionally...
The worst part in hindsight is remembering her past life and the whole "being raped by a bastard king wannabe" thing. Sex is literally just a function to her mentally at this point rather than any drive beyond her conflicted feelings for Theodore.
He was a normal guy that only fought because of the peach eye, and seeing everyone go from terrified by oni to "we have the advantage, now lets slaughter them all!" really didn't fly well with him, did it?
Seems more and more like he's either trying to set up Sari for failure somehow, or he's trying to pit Sari and Mikoto against eachother on their differences in mindset and goals. I wouldn't even be surprised if he wants the Peaches gone even if it means connecting everything else.
Starting to feel like Imperial hates his own species and wants to take the Oni down with him, with the peaches and other promising entities being his tools in doing so.
We're probably only seeing the surface of everything currently. The whole "merchant's lives are in danger if they don't bring her good gifts" thing was already a warning sign, she's probably suppressing negative info and executing anyone that displeases her whatsoever.
Maybe the sword has actual power, but the legend of it being a hero's sword is the real embellishment. The demons seem like they would be attracted to power naturally given how they already do that culturally, yet their failure to destroy it implies it does hold something.
This mother may have her own problems, but she's still utterly selfish and refuses to talk about her problems with even her own daughter until it hits the breaking point.