Aika is a smart and athletic high school girl. She is so competent that she successfully passes the salvagers license test, obtaining a C-class license. Yet, she is young and hotheaded, so much so that Gota still treats her as a child. Due to this personality, no one is willing to hire her for salvaging jobs. Since she had taken the trouble to get her license, she decides to post an ad in her school to attract clients.
This series was released backwards.
The release order is: Agent Aika, AIKa Zero then AIKa R-16: Virgin Mission.
The actual watch order is the reverse of that starting with R-16 and ending on Agent Aika.
Watch whichever way you want.