Min Yu Na (Yuna) lives alone in her apartment in Seoul, South Korea. Yuna is a 22 year old coffee shop owner. It was originally her parent's coffee shop but they gave Yuna responsibility to take over. Yuna's parents has been taking care of things on the other side of Seoul but Yuna's mother has recently passed, that's why she had to take care of the coffee shop. Yuna is secretly an assassin. Later she falls in love with a man named Kim Taehyung. Both are assassins but they both don't know that about each other. They both deeply fall in love but what happens when Yuna's contract is to kill Kim Taehyung...?