Jang Kun, Gwon Su, Woon Suk are average kids with average problems, but in the virtual world of Lost Saga, they go by the alias:user name Lotto, Boromir and Ah-Dol; they're heroes of the master class level or more so infamous troublemakers . They could become legends…if they can stop bickering long enough to level up. So whether it's werewolves running rampant or a gorgeous pair of thieves looking for revenge, our boys must be ready for anything.

Then one day Jang Kun, Lotto's real life self encounters a mysterious girl around his age, and ends up with her game card. What will he end up doing with it, and even furthermore how does it even connect with his gaming console? Is this more then what it seem to be, the mysterious game card with the name Yureka on it.