.hack//Legend Of The Twilight

Shugo and his twin sister Rena, two new players in The World, (a future online roleplaying game) are caught up in an unknown agenda. Unstopable monsters have started appearing and players that encounter these monsters fall into comas in the real world. Playing the limited edition characters, Kite and Black Rose, and the wielding the mysterious twilight bracelet, the two siblings must figure out what is going on and stop it before the damage escalates.

Synopsis from Anime News Network