Woah. Like that's all I can say. Woah.
The way you wrote the story was by far beautiful and grotesque (in a complimentary way!) what started out as a calming pretty cheerful first part devolved into such a mess where mysteries kept haunting us-- Honestly, it was absolutely breath taking the progression of the story became as well as the usage of background images and the way you draw Adonis.
I like how we see hints that MC is somewhat... Unique, like they can see things other people can't see (such as the rot in the apples), I'm wondering if they're more connected to that sort of grotesque side of life but they're just somewhat teetering off the edge, the line between their world and the other world.
Below will be theorizing, speculating, and plain out gushing about this wonderful VN~ So spoilers beware~!!
One thing I theorize is that either Adonis 'sensed' MC's presence and waited till they were settled within the town before making their move or if fate decided to intersect their lines (however, given how coincedental many things are and how Adonis clearly knows and is something more than what they appear to be... I have my doubts). Either way, I think that the long MC stayed with Adonis, the more exposed they became to gore, death, and decay that they otherwise probably didn't expect.
The more MC was exposed, the deeper they were entrenched to the point their senses (such as when Adonis says that they wanted to experiment with the human senses to experience art). I'm not sure if Adonis influenced MC to become... deranged in a sense or if MC was always like this, as though there was a deep-seated dark desire in them that only came to bloom when they were now fully exposed and influenced.
Then again, I'm wondering MC might be a Wendigo? Maybe part of them is and that's why they can see things nobody can see and feel hungry over decay and corpses...
Also, I liked how as the story progresses, Adonis takes a picture of MC at every turn throughout the photo walk where we can say that MC was being pulled deeper and deeper into the town's "other worldly" side. Like a lifecycle, where MC was just a baby or a fledgling at the start of the walk, before slowly being "corrupted" or maybe "corroded" as they become more and more aware of the supernatural entities, until we reach the ending where it seems as though MC's humanity is shedding and they indulge in a carnal or maybe inhumane desire by literally cannibalizing on someone (whether they are a ghost or not does not matter, she had a human shape therefore MC cannibalized that ghost or entity) and Adonis, who was much more interested in the rot, decay, and gore of the final stage of life, took many, many pictures of MC's final descent.
Before the cycle rewound and MC is now "normal" but not anymore, they got a taste of it... And they'll continue the cycle, following Adonis. I wonder if they're nurturing MC in a way, seeing them as their muse. It would be interesting to think but seriously, you did such an amazing job here!!
Aaa sorry for rambling so long I just really love it!!