Maybe a test subject for the "metaphysical program"

The siblings state that the test subject, is supposed to be the worldly manifestation of feucirl.
Edit: not actually, Teocida is just an “aptitude program.” So a candidate, for being the true manifestation, is what the player is.
The fact the dev immediately started a 3D game along the same line, means we’re not done with the story yet.

I was thinking that the player was either just supposed to be our self, or just be some random guy in-universe who got the program. However, their living/working conditions seem to be non-standard leading me to think they might be interested in, what we would consider, the occult. Just a theory of mine, but I think the Demiurge mentioned by the siblings may be after our player character + anyone who uses the sibling's programs. Demiurge, what maintains the physical world, would most-likely threaten subjects of the programs that propose metaphysical ideas to players. The various anomalies is what I consider to be the Demiurge's work. Furthermore, picture's they've taken show apparitions plus what they think is someone outside their window. So, my theory would be that the player is someone privy in metaphysical and has evidence what likely is the Demiurge has targeted them. I don't see any evidence that they would be the matriarch, since neither their self or the Demiurge would know.