I Collect Skill Fragments in the Demon World

Zhang Chen traversed to a mysterious world, where he can randomly collect skill fragments from demons and monsters—and add points to upgrade them infinitely.The first demon he meets is a fox, which is a good fox for it knows how to return favors. But, to Zhang, it is a bad fox, because it steals his food to return favors to his neighbor. — Description from novelcodex.org