Kusunoki Mia

Yua's twin sister that died in the Group Diving case.

Chaos;Head Noah Spoilers:
In Chaos;Head Noah, it is revealed that Yua is in fact the one that really died, not Mia. After that, she started suffering real DID unlike Takumi, whom she accused of having it, making herself believe that she was Yua while unconsciously blaming herself as the one that should have died instead of her twin sister.