I feel like I can follow roughly what was supposed to have happened by reconstructing it from the tropes it appears to be attempting to employ.
But the moment where the other (real) girl apparently really did show up to meet him and is making an angry phone call, and on top of it he's somehow figured out the protagonist is really his dog from who-knows-what hints, is completely incomprehensible as-is. It feels like multiple pages are missing XD
And of course we end with the "ambiguous" and "open" ending of for-now reversion to the usual status quo. (Honestly if she stays a normal dog thereafter that would be a super downer ending, given how long they've been together so far, and the known disparity in lifespans... But this sort of manga usually doesn't think that far.)