The 7z format is popular for digital media (like high-quality audio files) because it offers several advantages over standard .zip files:
You can search the ID "RJ140155" directly on DLsite.com to find the original product page, which will list the creator, cast, and description of the audio work. RJ140155.7z
When downloading files with an "RJ" prefix from third-party sources: The 7z format is popular for digital media