Resident Evil 2
A mysterious Asian woman encountered by Leon during his investigation in the Police Department.
While she says she is in Raccoon City looking for her missing boyfriend, she is actually an undercover spy working for an Umbrella rival lead by none other than Wesker.
Her assignment is to retrieve the G-Virus discovered by William Birkin.
As expected given her special training, her shooting skills and conduct have been refined to such an extent that she is able to remain calm and composed even in the most difficult of situations, silently carrying out her mission.
Her fateful encounter with Leon is among the most crucial of events in the series.
Height: unknown. Weight: unknown. Blood type: AB. Age: 24 (as of 1998 / Resident Evil 2).
Resident Evil 4
The mysterious Ada reencounters Leon 6 years after the events in Raccoon City. A capable spy with top-class combat training, nothing is known of her background.
Ada's current assignment as ordered by Wesker is to infiltrate the Los Illuminados cult, and retrieve a control Plaga parasite.
She does not inform Leon of her mission when they first meet in Salazar's castle, although she still assists and offers advice to Leon, albeit while maintaining a certain distance.
Height: unknown. Weight: unknown. Blood type: AB. Age: unknown (as of 2004 / Resident Evil 4).
Resident Evil 6
A spy operating in the underworld. Nothing is known of her background, even her name is a pseudonym.
She has crossed paths and cooperated with Leon multiple times, during both the Raccoon City incident and the abduction of the President's daughter.
Two distinct Adas make an appearance in Resident Evil 6: one who reveals herself to Leon at Tall Oaks, and the other to Chris and Jake in the Republic of Edonia, who is accompanied by J'avo and claims to work for Neo Umbrella (Carla Radames).
Ada has used Leon for her own goals every time they have met, and while they are not enemies there doesn't seem to be any clear indication of friendship or affection between them. From an outside observer their relationship must appear very strange indeed.
Height: unknown. Weight: unknown. Blood type: AB. Age: unknown (as of 2013 / Resident Evil 6).