Hmm!? That’s strange...
If you’re using NW.js, then you should just use the NW.js version directly.
Also, NekoGakuen_SteamworksPlus_en_US.js is only an early translation version. The current NekoGakuen_SteamworksPlus.js v1.3.0 already includes the English translation, so you no longer need the separate translation plugin.
As far as I know, you should only need the NW.js files I provided, NekoGakuen_SteamworksPlus.js, NekoGakuen_SteamworksPlus_SteamUserStats.js (for the achievement functionality), and steam_api64.dll from the Steamworks SDK for everything to work properly.
Also, please make sure that the Steam Achievement ID configured in the Steamworks backend exactly matches the ID used for the achievement function.