Kim Seolhyun is a famous idol singer. Yook Sungjae is a barista who is secretly training to debut as a singer. Since elementary school, Sungjae bothered Seolhyun. Thanks to AOA's sudden debut, Seolhyun managed to get away from Sungjae. Unfortunately, three years later, when AOA was really popular, Sungjae turned out to be Seolhyun's new neighbour. Something that no one ㅡexcept AOA members ㅡknows that AOA are actually real angels. They came from planet XOX. They each possess powers, which are the same. Meanwhile, Peniel is a sweet, brainy guy that is definitely Seolhyun's type. He's training to become an idol too, but also ready to become an actor. As Jimin, Yuna and Seolhyun were looking for the other AOA members, Suzy comes into the picture. There's something weird in Suzy's nature, that Seolhyun sensed. What'll happen if Sungjae knows about Seolhyun's little secret? Or worse fall in love with her?