Long ago, one of the supreme beings in the heaven tried to save humanity from the tyranny of the other gods but lost his life. During his last breathe, he passed his soul power so that one day a chosen one may follow his lead and take mankind towards the path of victory from annihilation threat. Thousand of years later, our hero regains power, fights evil nobles, and thus thrives in this new world with his over powered capacities.

Ever since moving to an in-game world after countless hours of VRMMO grinding, Yuna now calls Crimonia—the city where she started—home. While maintaining her reputation as a renowned adventurer, she continues to manage her businesses; but most importantly, Yuna spends time with the people she has grown to love. Nevertheless, this world has a lot more to offer the carefree adventurer. It is up to Yuna to discover these wonders, and perhaps help more people in need as she encounters their various plights.

After fanatically playing the VRMMO World Fantasy Online for almost a year, the shut-in yet relatively affluent 15-year-old Yuna receives a bear costume from the game's administrators. The outfit, while somewhat embarrassing to wear, turns out to have overpowered stats and effects that make her character significantly more powerful. After accepting the bear equipment, she finds herself transported to another in-game world that prevents her from returning to reality. Confused and unable to log out, Yuna sets out to explore this new environment. She rescues a girl named Fina from wild wolves, who then guides her to the city of Crimonia. With her eccentric bear attire, however, Yuna stands out wherever she goes, and alongside her boosted fighting prowess, her reputation quickly rises—to the point that people give her the nickname Bloody Bear. Undeterred by this change in her life, Yuna decides to take on the role of an adventurer and fully enjoy herself in her new world.

In a world covered by an endless sea of sand, there sails an island known as the Mud Whale. In its interior lies an ancient town, where the majority of its inhabitants are said to be Marked, a double-edged trait that grants them supernatural abilities at the cost of an untimely death. Chakuro is the village archivist; young and curious, he spends his time documenting the discovery of newfound islands. But each one is like the rest—abandoned save for the remnants of those who lived there long ago. For the first time in six months, another island crosses the horizon, so Chakuro and his friends join the scouting group. During the expedition, they find vestiges of an archaic civilization. And inside one of its crumbling remains, Chakuro discovers a girl who will change his destiny and the world inside the Mud Whale as he knows it.