Really love what they've done with Miko here. She's got this whole classic monster romance tortured-love dynamic going on with Hinako wherein she can't suppress an urge to feed on her, but also, in actively repressing that desire, is perhaps the most human of the cast, while Hinako, in her absence of anything resembling self-preservation, is both more human than instinct-driven beasts and unusual in that even humans often bow to that primal self-preservative desire when things get hairy, making her a subtler example of the human-inhuman paradox embodied by the other two rather than a mere 'pure' human. I also love how Miko, Hinako and Shiori are all united by the theme of a 'vow that clashes with your desire', wherein Hinako wants to join her parents in heaven (which might be an actual possibility, now that we know divine deities exist, which I hope homegirl realizes in the future), but can't opt for expedient death because of her promise to them; Miko's compelled to eat Hinako, but retains some scraps of a pride & responsibility as a guardian spirit as well as what seems to be a genuine adoration for Hinako; Shiori has none of these petty mortal moral compunctions and is majestically, regally inhuman, proud of her status as a creature far truer to herself than the rotting leftover and the lurking hypocrite, but is paradoxically vulnerable to the same vice that causes so many gods and demons to grow engulfed in complicated human affairs- her sense of taste is ironically perhaps the most rational, 'civilized' motivation that currently exists among the cast.
The main trio here is honestly among the strongest I've seen in any story I've read in recent memory, since they embody a lot of your standard triplicate idea divisions, such as the id-ego-superego or heaven-purgatory-hell, but never completely, always complex enough to have a nested contradiction that renders them more than archetypes. I could write essays on this, but one aspect in particular that fascinates me is how they're going to engage with the idea of divinity and guardian spirits, especially since they're confirmed to share some manner of biological link with the monsters. Are they different species? Are the monsters fallen angels who turned away from their purpose and became enemies of humanity? Are guardian spirits merely monsters who defected or were tamed? If a guardian spirit seems capable of degenerating into a beast, can a monster ascend to a higher status through noble deeds (this might end up being the endgame for Shiori, intentional or not, since mermaids are more often portrayed as sagacious, beautiful spirits than her Captain Cephalopod schtick, and her 'redeem Hinako's soul to the highest joys' plan seems like the kind of thing a guardian spirit would do if you removed the little subclaws at the end)? What happens if Hinako snacks on a monster? So many questions.
Also, Hinako being from a divinely-favoured family is probably one factor in her deliciousness to monsters (who I assume cropped up not recently, but were there all along and simply eradicated by pest control carried out by Miko, possibly when she was stronger or had help), and I love how Shiori and Miko's agendas regarding Hinako both clash with and support each other? Miko wants to keep Hinako alive and happy, but the process of living renders Hinako miserable, which might reduce her potential flavour by making her depressed and rotten, mitigating Miko's appetite, but also giving Shiori a massive window in which to prey on her, since her target's security is ensured at the cost of her flavour. And Shiori's whole convoluted 'be happy and love life so I can murder you at optimal flavour' is technically the best shot they have at making Hinako happy like Miko wants, since the prospect of a beautiful death seems to be her best motivator, but this also has the side-effect of both ensuring Hinako's death in the future (if Shiori isn't lying) and making her progressively more delicious, weakening Miko's already fraying restraint. Absolutely brilliant intersection of desires at work here, with each character being thwarted by precisely what they hold precious. It's like if No Exit was adapted into a lesbian romance catering to monsterfuckers, in which case I hope the endgame is polyamourous (polyamovorous)?
Seconding this analysis. All three play so well off of each other, and I can't wait to see what becomes of their dynamic with all this now out in the open.