Start the Viewer and see a visualization generated in 5 steps:
Next do the demo steps.
The "25" often indicates version 0.25 or a specific iteration of a continuous project.
Usually contains an .exe (if it's a standalone game) or a set of script files (if it's a mod for a base game engine like Ren'Py). Sissy_Adventure_25.zip
Files with these naming patterns are usually distributed on adult forums, imageboards, or specialized gaming sites. They often involve fetish-themed roleplay or "choose your own adventure" mechanics. The "25" often indicates version 0