of course I would agree with that
However, a quick search of canon material did not return any info about it.
Yea, nothing in the canon confirms or denies whether or not Nazrin was sealed away. In my own personal opinion, it isn't very likely though (but again, nothing's confirmed)
Interestingly enough, nothing's confirmed that Nazrin even gives a rat's arse about Byakurin in general. In fact, unlike the rest of Byakurin's supporters, who for the most part are innocent and quite confused when accused of things by the heroines, Nazrin even makes it quite clear that she's still happy to eat humans today (or at least, have her mice eat them). For Murasa, one of the heroines can't come up with anything to accuse her about besides the simple fact that she's a youkai (to which Murasa replies with the obvious defense that there's nothing she can do about THAT)
For all we know, Nazrin could conceivably just be a youkai who does the typical youkai things (such as say, terrorizing and eating humans) in her spare time, when she isn't carrying out orders from Shou or Bishamonten, and is only supporting Byakuren simply because of Shou's orders.
Again, there's nothing official to confirm that, but there's nothing official to even imply the opposite, either. If anything, Nazrin's willingness to eat humans sets her quite apart from the other dialogues in MOTF.
It also causes an interesting ladder, where the 1st stage boss is a typical youkai in Nazrin, the second stage boss is rather youkai-ish but only eats some human spirit instead of eating actual human, the next two youkai haven't really done anything bad to humans at all, the next youkai after that actually works with humans to the point that she's a substitute god for them, and the final boss wants to help usher in equality between humans and youkai. In Nazrin's case, a particularly interesting fact is that it's Nazrin, one of Byakuron's crew (or is she?), and not Kogasa, who's at the bottom of that ladder of human-youkai relations (since Nazrin and her mice are implied to actually EAT humans, which is a lot worse than just scaring them!).
