ONiely  oNiely (stylized oNIELy) is the first EP of Niel under TOP Media, released on February 16, 2015. The album is Niel's debut as a solo artist after over 4 years with the South Korean boy group Teen Top. Of the album's seven tracks, only "Affogato" was written by Niel. On January 5, 2015, it was announced that Niel would be making his official solo debut in February. January 27, on Mnet's "4 Things Show", Niel revealed a self-composed track "Affogato" from the EP. On February 1, TOP Media announced Niel would release an EP entitled "oNiely" on February 16. Niel collaborated with various artists for his EP, such as C.A.P, L.Joe, and Dok2. February 17 on the radio program, "Power FM's 'Choi Hwa Jung's Power Time," Niel said he had to go to the emergency room twice during preparations for the debut due to anxiety. On February 20 in the TV show "2TV morning" Niel's mother sent a video message stating "I found out from the news article that Niel had gone to the emergency room." On February 16, "oNiely" was released. "oNiely" reached number 1 on the weekly Hanteo Album Chart. It sold 17,205 copies on the first week. "oNiely" also topped the "Bugs album chart top 100" and Gaon album chart. On April 14, Niel released "oNiely" repackage "Spring Love". The repackage album debuted at number 8 on Top 20 Best-Selling Albums on the Taiwan's weekly Five Music chart and peaked at number 4 on Hanteo Album Chart. The official music video for the lead single "Lovekiller" came out on February 16 and features rapper Dok2. In the video, Korean model Yoo Seung-ok played the role of the "lovekiller". Much of the music video's inspiration came from Michael Jackson. Niel held the album's showcase performance at the Ilchi Art Hall in Cheongdam-dong, Gangnam-Gu, Seoul, on February 16, 2015. Televised promotions began on February 13, on KBS's "Music Bank". He also promoted his album in various radio programs. On February 17, Teen Top SNS posted a video titled "Running machine live".