Agent Aika, known in Japan as simply AIKa (アイカ), is a Japanese adventure OVA series.
On April 25, 2007 the first volume of the three-part prequel OVA AIKa R-16: Virgin Mission, detailing Aika's time as a teenager, was released in Japan. A remastered version of the original series was released also, along with a special Live Action edition of Agent Aika.
Tokyo has sunk into the ocean, along with most of the world, during a large-scale land subsidence. Aika Sumeragi is a salvager who works for a small company run by a father and daughter tandem. Alas, the company isn't exactly successful, and money is needed desperately. Thus, Aika accepts the very dangerous job of acquiring an artifact called Lagu for a hefty sum. The boss' daughter Aida Rion joins Aika on this particular mission, and the two set off.
Later on, Aika and Rion are captured by Rudolf Hargen—an effeminate but over-sexed man who wants Lagu and Aika (and just about every pretty girl) for himself. Hargen commands a huge battleship manned exclusively by droves of cute girls in mini-skirts (an example of what is often called "fan service"). Alongside Hargen is his obsessive sister Neena, who is jealous of Aika, as well as another salvager named Gusto, who's also after Lagu and has a crush on Aika as well. When Aika's special bustier is activated, she becomes a superhuman who can take on whole armies by herself.