Shortly after, on September 8th, it was announced that members Seyoung, Sangmin and Yongseok would be members of a new sub-unit, X HEARTS (크로스하츠).
Tak lama setelah itu, pada 8 September, diumumkan bahwa anggota Seyoung, Sangmin dan Yongseok akan menjadi anggota sub-unit baru, X HEARTS (크로스 하츠).