The YS adventure is set in a mystical world with dark secrets: Romune, the center of the YS world. Dark spells are ravaging the entire continent and people are talking about the 6 lords and the 6 ancient books sealed with magic spells.

The Man of Wings was not only the Absolute Being but also a God in the Eresia Continent. With the Man of Wings' ascension to heaven, the ancient civilization that had blossomed in the vicinity of Vartekal and Romune came to an end. The Europa Region, situated in the center of the continent was on the brink of disaster due to the evil stone's incredibly reckless acts and the copious amount of legacies left by the Man of Wings.

After nearly a hundred years, numerous kingdoms across the continent collapsed, one after the other with a multitude of evil monsters emerging. Worse yet, the remaining kingdoms fell into the hands of those monsters for almost 20 years. After years of slavery, Grey the brave hero and his 12 valiant soldiers appeared. They eliminated the evil gods who were masterminding those monsters, paving the ground for an Empire under the name of Romune. The Romune Empire continued to expand its domain to a degree where it held sway over most of the regions on the continent including Europa.

And now, you are here to re-connect the historical dots of YS. YS Online inherits the worldview of YS series.