This is a shorthand for enjo-kōshai (援助交際), which translates to "compensated dating." While the term historically referred to a social phenomenon in Japan involving dates for money, in the context of internet search terms and "links," it is almost exclusively used as a category label for adult content.
A "link" could imply a connection, a reference to a URL, or a relationship between different items.
:
If you are looking for a specific video or post, it is often associated with archived content from regional "Enkou" boards where "Solid" might refer to a specific contributor or a high-quality (verified) report.
Sites that claim to host "leaked" or "exclusive" links for specific codes often utilize aggressive pop-ups, malicious scripts, and phishing attempts to steal user data.
