The porn video tag "fairy-tail-erza" refers to a scene involving Erza, a character from the popular anime and manga series "Fairy Tail." Fairy Tail is known for its explicit content and fanservice, making it a common source for adult parodies and themed videos. In this tag, "fairy-tail" indicates that the content is based on or inspired by the anime/manga, while "erza" specifies that the scene features Erza as the central character. The viewers can expect to see explicit and erotic scenes involving Erza from the Fairy Tail series in such a video.