Does it look like the Kaldstrum exclusive ninja has the Na2 symbol on it's picture? If so, anyone fancy wildly speculating on how they may differ from JSA ninjas? (I know JSA have Ninjas and are Na2, but the info about the new Ninjas specifically said that they were the ones that chose to not join JSA) :-)
It does make me sort of hope that the use of Mercs is given a look at for N4 or C1. Mercs were this sort of grey area. Do I include them? Ask my TO? What about pick up games? CB makes a lot of characterful merc miniatures that may not make a break a list, but can be a fun rambo to paint up and toss into a game cause he looks pretty.
These belong to "Kunai Solutions" which appears to be a mercenary organization. I don't remember the source right now, but it has been mentioned that their Ninja focus predominantly on superior marksmanship, so I'd expect a higher BS and potentially some abilities to that effect, with reduced CC capabilities.
To answer your question about the difference: During and after Uprising, not all Ninja clans joined the Japanese Emperor in breaking away from Yu Jing. Some of the smaller clans, which weren't very competitive vs. bigger clans, decided to stay with YJ - no competition from Fukurou/Onishi/whatever the third big clan's name is, and a glut of contracts from suddenly hungry for ninjas State Empire. OTOH those smaller clans lost respect from their clients for being "untrustworthy" - they betrayed their liege after all, so some of them had to switch to mercenary work. One of those clans is Takemura Clan, whose public front is Kunai Solutions, a private security firm. Due to Takemura being a smaller clan, they don't have much in the way of martial tradition (or lost it after the exodus of Uprising), so they decided to substitute their melee swordfighter assassins with long-ranged shooty assassins (so switch from sane Eversor to Vindicaire). That proved to be a good move, because now even Japanese Oniwabans don't really want to tangle with them.