In regard to your question which spirit (killing or life-preserving, in short) is nurtured by Araki-ryu, the answer is both or either. The texts of the ryu have an essay, allegedly written by the founder (this is getting a little old - citing myself as a source, but see "The Origins of Araki-ryu" in OLD SCHOOL), in which he, Araki Mujinsai, writes about his teacher. In short he says that he got really strong, got intoxicated by his power, and embracing evil, almost lost his soul, recovering himself, sort of, at the last minute. If I'm correct that that man, Fujiwara Katsuzane was, in fact, Miyamoto Munisai, he, among other things, murdered his close friend at the behest of his daimyo.
That's one of the reasons, I believe why the "esoteric" traditions, which often are spiritual practices, are so important, because they provide a channeling - a vessel - which might contain the power to take life which one can, conceivably acquire.
Maniwa Nen-ryu? My usual caveat - I'm an outsider with opinions, not knowledge of the ryu. Nen-ryu has a history of some remarkably pugnacious indivduals enrolled in their ranks -but at the same time, its last headmaster informed me that protection is not only the ryu's purpose - (including protection of the village it resides, but the culture of the place) - but even its techniques are based on protection. They have a very distinct way of fighting in which they draw out a committed attack from the enemy and counter before it lands. NOT, you attack me and I counter, exactly. More like a counter-punch in boxing, that starts "later," but lands first.
I believe that Maniwa (at least when I last saw it a few decades ago) was able to maintain its integrity because it was so intertwined in the village culture that, on an unconscious level, one became a "Maniwa man" or "Maniwa woman" almost at birth. The esoteric training, which is, in part, to imbue one with a non-rational, 'instinctive" living out of the ryu in oneself, was occurring simply by living in Maniwa. They absorbed it.
However, in most cases - without the psychological, spiritual training which is the basis of the esoteria, you can't get under the founder's skin to grasp what he was trying to teach, and why he did it the way he did.
BTW - I've heard that Maniwa Nen-ryu has fallen on harder times. Last I heard, the high school club closed for lack of interest, and new young practitioners are few. The last soke died at a relatively young age - a fine man he was - so one worries for the future.
Best
Ellis Amdur
www.ellisamdur.com