A Fist Within Four Walls (2016)

Chor Au-kuen bears the grief of the loss of his family and returns to the walled city in hopes of finding his long lost sister, only to find out that the place he grew up in has become a lawless no man's land. Concealing his real identity, he creates a new identity and gets acquainted with a feisty hair salon lady boss, a dentist, and a common worker. To restore law and order in the walled city, Au-kuen unites everyone to form an association to collectively resist the villainous forces, but instead causes clashes between him and an underground fighting champion...