FitGirl Repacks are versions of video games that have been compressed to significantly reduce their file size, making them easier to download and distribute. These repacks often include selective language options, allowing users to choose which languages (in this case, Japanese) they want to install.
The primary reason for the existence of setup-fitgirl-selective-japanese.bin is efficiency. Modern games often have 5GB to 10GB of audio data per language. By making the Japanese files selective, FitGirl allows users who don't need them to skip that portion of the download, significantly reducing the total time and data usage required to get the game running. setup-fitgirl-selective-japanese.bin