So. Each of the three love interests is an aspect of Medea. Does this mean you could read between the lines and consider them to be aspects of Medea's backstory?
I like to think of it as Gravedigger-Mermaid-Princess, but I guess there is a specific order to it if you look at the way Medea describes the road ahead and the order that the signs are in (Mermaid-Gravedigger-Princess)

For my order, anyway, it could be like this. She was a gravedigger's daughter that survived a plague that killed everyone she knew and could have known, and so she started researching into gaining occult powers.

But then she found out that this trapped her in a region where she couldn't truly interact with others, and had to rely on summons as a way to find out what was happening in the real world.

Eventually, something in her snapped, and she decided that trapping her summoners in Faustian bargains was the best way to repay them, because being with her for eternity would be a better life for them than living one short human lifetime.


Alternatively, if it's the story order, then it could be she was just born a great and powerful witch, but grew enamoured with the real world, and arrived, only to experience a plague that took her newfound family from her.


Anyway, that's just me trawling for information in a short but interesting Yuri horror VN.