Well this game is not made by Unity, it is made by an self-developed engine called "NeoX" I guess. Meanwhile, since the signature has changed from "NXPK" to "EXPK", it is possible that netease has changed their packing method (slightly maybe?), making the unpack script not working any more. Also, changing the first four bytes won't make the script working again.
-Edit: A possible approach:
You could try to reverse "libclient.so" in the game's apk and see if you can find a Python bytecode called "redirect.pyc" which is used to "redirect"(?) the game resources. Here's one from Onmyoji on GitHub: https://github.com/YJBeetle/unnpk/commit/6bcfbdc2d97a3e0a774b8f00caa8638e8e0d7282