Walk on Air Skill is a skill that allows the user to walk on air for short periods of time. Li Jun got the skill from his Street Monk Class. Carl gets from his Enchanted Toe Ring of the Well-Balanced.
Story
Li Jun gets this skill from picking the Street Monk Class on the Third Floor
Book 6
SPOILERS FOR BOOK 6
Book 7
SPOILERS FOR BOOK 6
Carl receives the Enchanted Toe Ring of the Well-Balanced which has this Skill attached to it, but due to Shi Maria violently taking the skill from Li Jun he already permanently has it obtained.