Personally, I thought the finale was rushed, but mostly fine. Definitely have issues with the merger of the 2 worlds though; the lives of everyone from both would be wrecked, and if they thought Mina was a problem before, imagine how bad she'll be when she manages to amass an army of terrified anti-monster humans, equipped with weapons and technology that can't be neutralised with a spell.

And to be fair, noone, especially not Star, expected the merger to happen.