.hack//Tasogare no Udewa Densetsu

Welcome to The World, the most advanced online game ever created. Fourteen-year-old twins Rena and Shugo are two middle-school students who enter The World as level-one game characters--and now they're ready to take on anything...or so they think. When Shugo's character dies, he is transported to another level where he is entrusted to bear the Twilight Bracelet by the mysterious Aura. Shugo must find out who Aura is and why she gave him this powerful weapon to protect his sister from the dangers in The World.