[Shinobi Killfist]

So you have a threshold of -1 and get a free hit. Is that a net hit for drain calculations on spells like improved reflexes or is it some weird free hit thing?

[Kiirnodel]

Against a threshold of -1, zero hits is considered 1 net hit, additional hits would be more on top of that. Determine the effects of net hits normally.

It is a "free hit" only in the sense that your net hits is 1 more than your rolled hits.