[Valky]

Spoiler:

“Did you tell broth… no, that person?” “Of course. Don’t be deceived. His thoughts are anything but conventional .There’s no question that he doesn’t love me as a mother.” Within her voice, Miyuki could detect a drop of frustration with her son’s lack of love toward her.

Somehow from this line I got the impression that their mother actually give a damn about Tatsuya.

If she really did give a damn, then about the experiment at age 6, it could be another form of love from their mother. Twisted love, maybe. Well, can't really blame her since Tatsuya couldn't do magic at that age and considered defect/failure, and there is no place for such failure at their family so in a way she did it for his sake in order to save his life since he would definitely die if she didn't.

I'm not drunk, I think.