Kim Myungsoo a full time agent of the SSD (Seoul's Security Department) alongside with his group Infinite which is being led by Kim Sunggyu are given a mission to catch an assassin with a code name Knightwind. While at this mission Myungsoo met Kira a girl who lives at the apartment next to his, she is so strange she doesn't talk much, acting so mysterious, even when Infinite tries to be friend her she just say she doesn't need friends, but that what makes Myungsoo more interested.

Can Myungsoo break the wall of ice the ice princess built herself? Will this affect thier mission when they found out that Kira has something to do with Knightwind? Will a full pledge law abiding officer let his feelings get through his mission?