Assuming that SONE-026 is related to adult content, it's possible that it refers to a specific video or a series of videos. In the adult entertainment industry, it's not uncommon for production companies to use codes or identifiers to categorize their content. If SONE-026 is indeed a video code, it's likely that the content is restricted to mature audiences only.
While the primary audience is located in Japan, the distribution networks for such media often result in international visibility. SONE-026