[4] Jonghyun remained musically active as the vocalist of Shinee and as a solo artist until his death on December 18, 2017, when he died by suicide.

[16][17] In October 2010, Jonghyun was one of twenty idols from various South Korean groups that recorded the song "Let's Go", which promoted the 2010 G-20 Seoul summit.

[21] Jonghyun won the first round and defeated his labelmate, Yesung of Super Junior, but left the show after the first episode due to his busy schedule.

[22] The show subsequently came under fire from viewers, who claimed the program's harsh elimination method and structure left Jonghyun in tears on stage.

[23] In October 2013, Jonghyun debuted as a composer with the track "A Gloomy Clock", which was included on IU's third studio album, Modern Times.

[29] In July 2014, Jonghyun began a segment on his radio show where he wrote songs based on stories submitted by listeners.

[30] In August 2014, fellow Shinee member Taemin released his first EP, Ace, for which Jonghyun wrote the track "Pretty Boy".

[35][36] On January 9, television network Mnet confirmed that Jonghyun would appear on the entertainment program 4 Things Show.

[40] Jonghyun released a new compilation album of self-composed songs originally performed on his radio show MBC Blue Night.

Each concert featured a different guest, including Shinee's Onew and Taemin, IU, Zion.T, Jung-in, Lim Kim, Oksang Dalbit, Coffee Boy, Nine, Lee Ji-hyoung, Soran, and poet Ha Sang-wook.

[43] Jonghyun appeared on the debut of the Mnet program Monthly Live Connection, which brought together two artists from different musical backgrounds to collaborate on one song.

[46] The same month, Jonghyun was selected as one of the top five K-pop idol vocalists by a survey completed by 40 anonymous music industry officials.

[47] Jonghyun published a novel, titled Skeleton Flower: Things That Have Been Released and Set Free, on November 19, after previously selling it in limited quantities at his concert.

[57] The decision came after a lengthy discussion between Jonghyun and the show's staff, who stated, "It's disappointing, but because Shinee's Japanese and North American tour is about to start, he decided to leave.

It was a space where he could explore new things, express himself and connect with the public on a deeper level: ''Before, I think I was more comfortable being "the singer Kim Jonghyun."

[59] Jonghyun held a series of 20 concerts, titled The Agit (The Letter), between May and July, 2017, at the SM Town Coex Artium in Seoul.

[62] Around the same time, Jonghyun was also working on his new album, which was set to be released in January 2018, and had also finished filming the music video for the lead track.

[66] Poet | Artist debuted at number 177 on the Billboard 200 with 5,000 equivalent album units, making Jonghyun the fourth Korean soloist to appear on the chart, after BoA, G-Dragon and Taeyang.

[79] Later that day, at 4:42 PM, Jonghyun's older sister, Kim So-dam, made an initial call to emergency responders, reporting that she believed he intended to kill himself, because he had sent her a number of messages on KakaoTalk with words such as "last goodbye" and "say I did well".

He received emergency treatment, but failed to regain consciousness and was pronounced dead at the hospital at around 6:32 PM, aged 27.

[80][84][85] Investigators believe he died from inhaling either toxic fumes or smoke, as they discovered coal briquettes burnt on a frying pan upon arriving at the apartment.

[84] The police stated that, at the request of Jonghyun's family, a post-mortem would not be carried out,[86] and they declared his death a probable suicide.

[88] Celebrities, such as BTS, IU, BoA, Girls' Generation, and Exo,[89] and fans attended the three-day public funeral.

[105] Jonghyun's death opened discussions about the harsh and competitive nature of the entertainment business in South Korea, as well as mental health.

[111][112] Jonghyun's appearance on the variety show Night Goblin was scheduled to air on December 24, 2017, but JTBC decided not to broadcast it.

[124] Jonghyun's musical style was considered to be unique, and he received praise for writing and composing the majority of his solo tracks.