Something I have considered a lot about their dynamic is that Shion does seem to be written with the intent of caring for Mizuki. It's a very classic "hurt people hurt people" dynamic, I think, in which she has gone through immense suffering, which caused her to form a persona and ideal set that prevents her from more suffering. Her treatment of Mizuki, in some ways, seems to be a leash that is made to prevent him from suffering in the same way, while also existing as a way for her to express her pain onto someone dependent enough on her emotionally and physically that she did not ever think they would leave. (After all, suffering does not a good person make. Just one that has known suffering.)
This being said, I considered the idea that he would, especially in the beginning as a recently orphaned child, go to her for comfort. She would never allow it, I personally believe, unless she had a way of displacing the entirety of the decision onto him. Hence this concept, in which she is charging or something akin to it, and Mizuki comes and crawls into her arms, dragging one of them over him in the facsimile of an embrace. She would never lie down like this in a totally unaware state, she's too paranoid. But since she can tell that it is only Mizuki, she remains in her "sleep mode", such that she can claim it was in no way her decision.
