Rainbow Eyes (2007)

Country: South Korea
Release Date: Dec 27, 2007
Duration: 1 hr. 39 min.
Content Rating: 18+ Restricted (violence & profanity)

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.