Hi.

If the installation was simply to "After that, drag and drop the the files into data/chara/ and data/chara/CMN", then you can uninstall it by removing those files from the game's directory. The data directory was created by Eternity's tools just so you don't have to overwrite the game's real data.cpk folders. Whatever is inside Eternity's data takes precedence over game's real data. So the simple fix is to remove the downloaded files from the path's destination and be done with it. If that doesn't work and/or you are uncertain about what files to remove from inside the data folder, you can use Eternity's Mod Installer's function to Clear Installation. That will remove all mods and create a new data folder that will replace the old one from Mod Installer.