It wasn't.
It isn't quite clear that he actually
uses it, but he refers to it in his training times as a kind of dream of his being closer upon reality, mastery wise...but the whole thing went kaput when he went to the magical world and tried the quick way instead.
However, all the synthesis is still there. It's like I said...
"...this a prime time for him to expand upon that art, which could be difficult, seeing as it is an opposite from the other..."
I suppose I confused some by saying that he had it, when in fact I meant he had the
groundwork for it, sorry there, I was working at the same time I was typing on dismantling a computer room.
He has martial arts, the way of finding inner peace, the experience in controling energy from magic and the war song...if he can get a grip on his emotions using these tools...making himself nothing, being one with the world instead of singling himself only and tuning the world out should be easy...he is a technical genius after all...but I'm not saying it would be easy...then where would the fun be?!
As for the Nodoka bit, yes, I mean the seals. Don't they have to be powered by something...and don't they have a slight energy signature? Or are they one hundred percent efficient and untracable?