To put it simply, "fc2ppv3966770mp4" refers to a specific video file from the FC2 platform, purchased through its Pay-Per-View (PPV) system. The "3966770" is its unique identification number, and "mp4" is the common digital video format. The more mysterious "upd" typically indicates that this is an updated version of the file, perhaps with better quality or a newer revision. Think of it as a label used in online communities to note that this isn't the very first version released online.

: Forums, bulletin boards, and cloud-storage syndicates use these update tags to notify their user bases that a previously dead link has been refreshed or replaced with a high-definition alternative. Media Formats and Streaming Optimization

FC2 is an established web services company that hosts a massive user-generated content market, particularly known for its decentralized adult entertainment section. Unlike traditional adult video (AV) studios in Japan, the PPV marketplace allows independent creators and amateur videographers to upload content directly and set their own pricing models.