From Tokyopop:

In real life, Roto, Boromid and Ah-Dol are average kids with average problems, but in the virtual world of Lost Saga, they're heroes. They might even become legends... if they can stop bickering long enough to level up. Whether it's werewolves running rampant or a gorgeous pair of troublesome thieves, our boys must be ready for anything, because in Lost Saga nothing is what it seems and murder can happen with a click of a mouse.

The series centers on the main character Jang-Gun and his friends along with their virtual reality avatars in the computer game world called "Lost Saga". When Jang-Gun logs on as a different character, he "Creates" an AI with a personality from the hacked disk he found when renewing his appearance for his once a year renewal process. Yureka is a flutter-brained, but advanced, AI with powerful stats and a real-life doppelganger. It is his turn to see just how deep his immersion in the virtual world goes.