My 1.5-Billion-Won Item

In the VR game Legend World, people earn money by selling items in the real world, but ordinary player Yak wants more than just making ends meet. Then one day he gets a mysterious reward, Gigantes Dark, a pet-class item worth 1.5 billion won! Finally thinking he's made it, Yak is dismayed to learn that, as a pet, Dark can't be sold. However, as there's no limit to how powerful Dark can become, Yak decides to raise him. Can Yak be a good parent for Dark and rise to the top of the Legend World?