Black Suit

It was released as the album's title track on November 6, 2017, by SM Entertainment, Label SJ and Genie following the revelation of multiple video teasers.

The song was composed by Martin Hoberg Hedegaard and Coach & Sendo, while its lyrics was penned by Lee Seu-ran, Jo Yoon-kyung, Oh Min-joo, Lim Jeong-hyo and ESBEE.

The song told the story of a man who steal people's heart while wearing a black suit, inspired by the character Lupin.

A commercial success, the song peaked at number 23 on Gaon Digital Chart and was downloaded over 92,000 times in the month of its release in South Korea.

An accompanying music video depicting a heist conducted by the band members during an auction of a black suit, directed by Rigend Film, premiered the same day as the song's release.

In July 2015, Super Junior released the compilation album Devil to commemorate their ten years debut anniversary.

[6] At midnight of September 27, a photo containing the cryptic word "D-40" and "SJ Returns" was posted on Super Junior's social media accounts.

[9] On October 9, 2017, SJ Returns, a reality program that documented the band's 120 days of preparatory period leading up to the release of their upcoming album started airing on Naver TV and V Live.

[10] "Black Suit" was first introduced in episodes 17 and 18 of SJ Returns which aired on October 19, 2017, as one of the five songs shortlisted by their agency's A&R team as the lead single candidate of the upcoming album after conducting blind test involving over 100 demo tapes.

[16] The single featured the voice of seven out of eleven members of Super Junior, namely Leeteuk, Heechul, Yesung, Shindong, Eunhyuk, Siwon, and Donghae.

[37] The Korea Herald writer, Hong Dam-young, on her review said "[Super Junior's] powerful vocals blend well into the song's pulsating swing vibe".

[26] Shin Mi-rae from MBN also commented on the song's composition, saying that "the melody of the chorus captivates the ears with its addictiveness that makes it imprinted on you the moment you hear it.

"[40] News publication Ten Asia described the song as a result of the band "pursuing a more sophisticated style" yet still "showing some of their music colours".

[52] The band members play various roles in the music video; Leeteuk as the auction host, Heechul as an investor, Yesung as a courier, Shindong as a rich man, Eunhyuk as an appraiser, Siwon as a client agent, and Donghae as a bodyguard.

[61][62] The live performances only featured six out of seven available band members as Siwon decided to step back from participating in the album's promotional activity.