Harley is a 16-year-old convict from Destiny City imprisoned for murder. He is not initally known to wield the Keyblade, but Sophia (disguised as the mysterious Phade) gave him the ability by shaking hands with him when he woke up in Traverse City's Iron Will Tavern & Inn, then owned by Sophia. In Traverse City, where authorities are seeking him, he goes by the name Slim except in the Ninteenth District, where his current safehouse is.
Harley has brown hair until the opening cutscene of Traverse City, when he dyes it ash grey to hide, and grey eyes. He uses contacts in Traverse City to make his eyes appear green. In prison, he wears a white T-shirt and jeans, but Phade/Sophia gives him more clothes to help him disguise himself. In Traverse City, he wears a bulletproof breastplate and pauldrons over a black sweater, khaki cargo pants, greaves, and gauntlets, and a black bandana around his neck. His sweater's hood pokes out from under the armor.
Until he gets his Keyblade, Crash Star, Harley fights using the Hand-and-a-Half Sword, a plain sword with a white grip. He also has a handgun called the Nine, a compact semi-auto over-under shotgun called the Shorty, and a choice of dual submachine guns or a hybrid assault/sniper rifle, called the Dual SMG or HRO-R (Hybrid Range Ops Rifle, pronounced "Hero-R")
Harley's fighting style is Aggressive-Type, meaning he takes the offense while not being controlled. Due to his being Aggressive-Type, Harley cannot learn Guard or Dodge Roll, but gains bonuses to Manic Dash and Vortex. Visual indicators of his fighting style are his tendency to step forward during each attack and his use of long, heavy swings.