At this point, we can see that all events in the story either link to each other or foreshadow one another. I have a hypothesis to explain what has been happening here.
The aunt is actually the girl Shiori used to give her flesh to (as I’ve guessed long before). She seeked revenge because Shiori gave her the immortality she never wanted. But since she couldn’t really harm Shiori, she shifted her target to Hinako, the one Shiori loves and cares for the most. By doing this, she could destroy Shiori completely.
Remember Hinako’s family accident happened shortly after young Hinako met Shiori? I think it had something to do with Azami, she could be the one who caused the accident after she realized Shiori had formed a special connection with young Hinako. She had planned everything carefully as she intentionally left Hinako alive to made her suffered and wanted to die, which then led to Shiori’s promises to eat Hinako and the development of their relationship. She had been acting as Hinako’s aunt in Ooshima since then bc she wanted to witness Shiori’s suffering after Hinako’s changes (This was proven by the fact that Azami had appeared in the beginning of the story even before Shiori, if you noticed the text messages in chap 1. There was no reason for her to do that unless all I’ve said above was true). But I think she wont stop there. She might want Hinako to get eaten by Shiori since that will be Shiori’s worst pain and also the end of her revenge.
For those who wonders why Azami revealed herself in this chap, I think it was bc she wanted Shiori to know that she was the one behind all of this, and everything was not just an accident or coincidence. It was like an announcement of revenge, which reminded Shiori’s of her sin in the past, and now they all have to pay for it.
