Rainbow Eyes (Movie) (2007)

Kyeong-Yoon (Kim Kang-Woo) and Eun-Ju (Kim Gyu-Ri) investigate a grisly murder of an affluent entrepreneur. The victim was slashed over 20 times and there’s blood everywhere in his apartment. The killer was careful not to leave behind incriminating evidence, but nevertheless, a strand of the killer’s hair is found. The police are then able to determine that the killer is male and has AB bloodtype.
Shortly after the first grisly murder a second murder occurs. The victims seem to be unrelated but the modus operandi seems the same. When the police delve deeper into the victims’ background they discover that the two victims were stationed at the same military base many years ago. A month prior to their discharge they were transferred to another base along with a third man by the name Jay Bae. The police now believe Jay Bae could be the next victim or the killer. Their investigation has only just begun.