She is the stepsister of Otacon and the creator of GW, the AI installed in Arsenal Gear that was designed to control the flow of information. She got involved with Arsenal Gear seemingly to get revenge on Otacon, as she blamed him for not rescuing her when she almost drowned with her father in their swimming pool when she was a kid. Otacon had not known that she needed help because he had an affair with his stepmother, Julie, and was in his room with her at the time. Their father did not survive the ordeal. His death was actually a suicide, triggered by his discovery of Julie and Otacon’s secret relationship. Emma developed a fear of water after this traumatic experience.

Emma was taken prisoner during the Big Shell incident in 2009, and was eventually rescued by Raiden. However, she was attacked by Dead Cell member Vamp, and died shortly after being reunited with her brother and installing the virus to destroy GW.