Shin Sekaiju no Meikyuu: Millennium no Shoujo

The Highlander's help is requested in Etria, where an organization called the Radha hires him to explore a labyrinth. Soon, the highlander discovers an amnesiac girl in a futuristic tube, and meets some fellow investigators from the Midgard Library. The group of them team up as a party to continue their exploration!

(Source: MangaHelpers)