When you find the slug, there are two possible endings: either you kill it, or you surrender to it, becoming corrupted and likely becoming part of those monsters...
Like the first game, I think the creator wants us to imagine what that could mean, that Lelia would never be corrupted and that she's doing the right thing, or that the player really just wants the protagonist to suffer and be raped; it all depends on each person's point of view.
The ending isn't explained or anything like that, leaving everything open-ended. the next update will probably have a more explanatory ending, I think.
