indeed, however that would only make sense if they were fighting against each other and stealing the losers power. even then though i'm not convinced they'd be close enough in power due to being so far away form the epicenter of the event. just look at the explanation for why the corrupted vessels are stronger than the normal ones. distance matters.
however that being said some of the meta physics in the game are pretty wonky. especially regarding the MC. but that's to be expected of a smut game i guess. gotta play to the fetishes rather than stuff making logical sense! LOL
Brief disclaimer: I haven't beaten the game yet, so I apologize in advance if I suggest something the story already addresses.
And the cliche with that, in particular, is that the first BBEG being defeating was either planned or needed for the next BBEG to come into power. For example,
maybe there's a counterpart to Nori (that neither her or the director were aware of) that was also suppressed as a side effect, and lifting Nori's suppression means the other entity is now also unbound. Alternatively,
there were predecessor test subjects or whatever with an unusual power that were either under the director's control or hid their existence until he was defeated. Thirdly, something that shouldn't be possible happens, because literally magic is involved and the events of the game had no precedence.