The idea is okay and was wrapped up nicely in the end, but the build-up needs a LOT of work. Could've been an 8/10 anime if they wrote it better. The worst part for me, personally, are the character introductions. They're all over the place, and if I didn't finish this I wouldn't have even known why they were introduced.
My initial rating was a 4, but bumped it up to 5 for the ending.
