I have a hunch that the author will make the lesbian girl be uber evil and vile to "justify" her death by rape.
Going by the ending of this chap, the author will have the lesbian girl rape the possessed twin tail girl for extra "tots evuls" points.
Hmm, K here is my wild random theory:
The MC HIMSELF got possessed at some point by a ghost, and in his possessed state, did something that killed his mother.
Perhaps when he was younger, he didn't have full control of his power, and it backlashed onto his own body somehow.
I've seen some of the fanbox chaps over the 7 seas.
Its kind of like r18 version of 1:39 male to female ratio where they act like completely different characters.