Trusted digital preservation repositories archive older software for historical purposes, often ensuring the files are verified clean of malware before listing them.
The phrase "serial number verified" might come from cracked versions where the cracker included a "verified" serial in a text file, or it could be from old forum posts where users shared codes and others "verified" they worked.
Instead of searching for dangerous activation cracks, it is highly recommended to look for legitimate, modern adult gaming alternatives available on safe, mainstream platforms. Many modern visual novels and adult card games are officially distributed on trusted platforms like Steam, Itch.io, or GOG, where you can download content securely without risking your computer's safety.