MusicWolf published a step-by-step guide on how to install it on the previous page:
Apparently the crack of the game requires that it has been installed, because it finds for some key/s that the installer generates in the registry. And apparently also if it detects that the game has already been installed because of some data present in the registry, it dims the option and does not allow reinstallation until the previous installation is completely removed.
And in theory if the option appears dimmed to reinstall it, it's because the data it generates in the registry already exists, so try loading the image arukazoku.iso, or open that iso with 7-Zip or WinRAR, select all the files contained in that iso image, and copy&paste them in the root folder of the game overwriting its contents, and then unzip first the contents of the Patch Eng v9977. rar that applies the crack and patch with the translation overwriting the files arukazoku.exe, Arc01.dat and Arc04.dat and others that overwrite and replace, then unzip the content of the 或ル家族ノ姦系図 (NoDVD EXE) AlphaROM 3. 3汎用 signup tool 110722.rar which is a fix of the crack also inside its root folder, and test if it runs the game by running the game start.bat, which applies the crack and also a Japanese language emulator.
And another VN from TinkerBell that uses a similar crack and circulates as a portable with the content of the game already installed with the crack applied, doesn't work either because apparently some key is missing that needs to be present in the registry and generates its installer, and that portable version doesn't bring any *.reg file to be able to export that missing data in the registry.