Into the Mirror (2003) on Netflix

Plot summary

Woo Yeong-min blames himself for the death of his partner Young-ho during a hostage situation, so he resigns from the Seoul Special Operations Force and joins the security company SecuZone. His uncle Jeong Il-seong owns Dreampia, an immense department store rebuilt after a fire in which many employees died, and hires Woo as its head of security shortly before the reopening. Families of the fire's victims protest the reopening and demand compensation. When an employee dies in the store after hours, Woo begins his own inquiry into the deaths, which are taken for suicides and all involve mirrors. Detective Ha Hyeon-soo, who holds Woo responsible for Young-ho's death, arrives to run the official police investigation and refuses to cooperate with him.