The old town of Tokyo is buried under water following a terrible catastrophe which has occurred several years before. Aika and her young partner Rion work for an agency specializing in the recovery of old relics, but the owner has serious financial problems. This is why it was decided that Aika again take up her old activities as a special agent...

Aika with the assistance of her friend Gusto, succeed in escaping from the ship, leaving behind Rion. Her last combat left her weakened and she is no longer any match to face Hagen and his crew. During this time, Rion and Maypia, a spy whom they met, try to escape, but the projects of Hagen have already started to be carried out...

An operation disguised in the form of collecting information on board a ultra-sophisticated plane, is worked out by the Delmo organization in order to secretly study the aptitudes of Aika for combat to discover her weaknesses. The latter not suspecting the trap which awaits her, accepts the work which is proposed to her.

During her overtime at the office, Aika is suddenly attacked by an agent of Delmo which manages to escape afterwards. Little time after, the building in which Aika is in explodes. Rion and her friends attend a funeral for their friend. With the assistance of Maypia and Gusto, Rion decides to infiltrate the enemy base to avenge the death of Aika.