Big Bang Hallelujah ( OST IRIS)

National Security System (NSS) Top 707 agents Hyunjun and Sawoo are blood brothers who swore to trust each other and unchanging friendship for life. They meet agent Seunghee there and both fall in love with her. But Hyunjun and Seunghee become close and Sawoo fights to hide his feelings for Seunghee. One day, they are immediately sent on a mission to Hungary. When they successfully finish off their job with immaculate teamwork and are celebrating it, a message arrives to Hyunjun asking him to meet i