Some confusion, so the "Summer Medusa" is a Lancer, but is the form of Medusa most often referred to as "Rider," not "Anna," the form of Medusa who is normally a Lancer. This is confusing.
Note: I haven't played the Japanese version of FGO.
EDIT: So, I removed the Medusa_(Lancer)_(Fate) tag, as that is for "Anna," should this be something like "Medusa_(Swimsuit_Lancer)_(Fate)"?