To play: download ng2recomp-v1.0.16-win-amd64.zip below, unzip it anywhere, run ng2.exe and point it at your own copy of Ninja Gaiden II (a disc image or an extracted disc folder) and, if you have them, your DLC packages. The zip holds the executable, the runtime, the Visual C++ runtime it needs, the controller database and the texture tools including the AI upscaler engine - and no game assets or data of any kind. The executable contains the game's code in translated form; without your copy of the game it does nothing. Updating an existing install: unzip over it; game\, dlc\, user\ and your settings are never touched.
Added - the game checks for updates on launch and can install them itself
On start-up the game now asks GitHub whether a newer release exists and, if one does, shows a prompt: Update now, What's new, or Later. Choosing to update downloads the release zip and, after a confirmation, closes the game, swaps in the new program files and reopens - you never visit the website or unzip anything by hand.
The installer only ever replaces the program (the executable, the runtime and GPU plugin, the Visual C++ runtime, the controller database and the texture tools). game\, dlc\, user\ and your settings files are never touched - the same contract as a manual "unzip over it" update.
The check is a background network call that never delays the boot, and the prompt appears only when there is genuinely a newer version. A new setting, "Check for updates when the game starts" (on by default), turns the whole thing off for anyone who would rather keep launch offline; the F10 settings menu also has a Check now button and shows the download progress and the same install button. The launcher talks only to the GitHub releases API and downloads only the release asset over HTTPS; nothing else leaves the machine.
Because this is the first version with the feature, an existing v1.0.15 install cannot offer it to you automatically - update to v1.0.16 once by hand, and from here on the game keeps itself current.
The runtime and GPU plugin are the stock pair, unchanged since v1.0.13.