High school student Aika Sumeragi with her sharp mind and athletic body has passed the C-class Salvager test and got herself a C-class license. Despite being a sixteen year old teenager now, she is still being treated as a child by Gozo. Having finally gotten a license, Aika starts putting up posters offering her Salvager services. At that time, her classmate and president of the Treasure Hunting Club, Eri Shingai, posts a request. Aika gladly undertakes Eri’s request and boards Eri’s private cruiser. Onboard, she learns about a mysterious girl called Karen who is the reason for the request. That very night, Aika is assaulted by high school girls and Karen is almost captured. What secret does Karen hold?