Atlus Etrian Odyssey Untold : The Millennium Girl

The hero is a young Highlander, a member of one of the many clans from the Highland area, who receives an unusual request and travels to the town of Etria.
The request was to "investigate an abnormality occurring in Etria."
The town`s ruling council has sent for a Highlander to search for the source of a series of mysterious earthquakes and sounds that has begun to trouble the city in recent months. In the course of his investigation, he meets an amnesiac girl named Frederica.
A trio of researchers from the Midgard Library, an institution several settlements over, has come to Etria to seek out the same abnormalities. After a chance encounter with the three, they introduce themselves as Simon, Arthur, and Raquna. It soon becomes apparent that there is a need for all of them to delve into the challenging wilderness of the Yggdrasil Labyrinth, which has some deep connection with a set of strange ruins.
What could these abnormalities be? All the keys to this puzzle remain locked in the memories of the girl...