Killed along with her parents one year prior to the start of the series, Fuwa Aiko was Mahiro’s step-sister and Takigawa Yoshino’s girlfriend. Both boys were still unable overcome her loss and are determined to avenge her death. It is later hintes that she is the key to many unanswered mysteries surrounding them, including the culprit behind the murders.
And this would be Chinese cosplayer Tracy Miroa from China! Her eyes are quite something indeed, and this photo really draws you in. Thanks to Hikari for sending this in!
Source: ~Addiction to Anime~