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 doe

Ito ang kwentong hindi inasahan nang marami, nagsimula sa isang sulyap, isang hindi inaasahang pagtatagpo, isang kaway na nagpabago sa buhay ninyong dalawa, isang tambalang nagiwan ng malaking marka sa kasaysayan ng telebisyon at social media.