AIKa R-16: Virgin Mission is an anime OVA series by Studio Fantasia. It is the prequel to the Agent Aika (AIKa) OVA series, also by Studio Fantasia. The series takes place 10 years before the events in Agent Aika. It is followed by a sequel OVA series, AIKa Zero.
This series also celebrates the 10th anniversary of the original AIKa OVA.
Plot: High school student Aika Sumeragi, with her sharp mind and athletic body, has passed the C-class Salvager test and gotten a C-class Salvager license. Despite being sixteen years old now, she is still being treated as a child by Gozo. Having finally gotten a license, Aika started putting up posters offering her Salvager services. At that time her classmate and president of the Treasure Hunting Club, Eri Shinkai, posted a request for her. Aika gladly undertook Eri's request and boarded Eri's private cruiser. Onboard she learned about the mysterious girl called Karen who is the reason for the request. That night Aika was assaulted by high school girls and Karen was almost captured. What secret does Karen hold?
(source: Wikipedia)

Related anime: AIKa