2010–2017: Musical theatre, acting debut and solo activities
In 2010, Onew tried his hand at songwriting and, together with his bandmate Minho, wrote the lyrics for the song "Your Name" from Shinee's second studio album Lucifer. In addition to music, Onew became an MC of two programs—KBS2's Night Star, which he co-hosted alongside Shin Dong-yup, Yoon Jong-shin, movie director Jang Hang Joon, and Leessang's Gil, and MBC's Show! Music Core. Since his first job as an MC, Onew has hosted various events, such as Dream Concert, Incheon K-Pop Concert and Mnet's special event in Taiwan called Nihao Taiwan.
Onew starred in various musicals starting from 2010, debuting in the musical Brothers Were Brave alongside singer Lee Ji-hoon. He then starred in the Korean production of Rock of Ages playing the lead role, Drew. Onew has also showcased his acting skills via television like having a cameo role as a clumsy doctor in the drama Dr. Champ. He appeared in the drama's final episode. He also had cameo roles in the dramas Athena: Goddess of War, Oh My God x2, Pure Love and sitcom Royal Villa. In August 2012, Onew recorded a song titled "In Your Eyes" for the drama series To the Beautiful You. Onew also sang the soundtrack "Moonlight" for the drama Miss Korea. The song was released on January 3, 2014.
On January 14, 2014, his participation in the Borneo edition of the reality show Law of the Jungle was confirmed. He was also originally cast for the Brazil edition, but had to be replaced because of schedule conflicts. In addition to his group activities and his job as a MC, Onew gained experience in radio hosting and took over shows like Kiss the Radio, a popular radio program aired on KBS Cool FM which is hosted by his labelmates Super Junior. In June 2014, he was originally planning to appear in the musical Singin' in the Rain but was unable to join as he underwent vocal cord surgery.
In 2016, Onew was cast in the drama Descendants of the Sun, which starred Song Hye-kyo and Song Joong-ki. He portrayed first-year resident Dr. Lee Chi-hoon, a junior of Song Hye-kyo's character. The drama became a huge success, especially in China, where the series reached more than 2 billion views on the Chinese streaming site iQiyi. In Korea, the drama became a massive hit as well, surpassing more than 30 percent viewership ratings nationwide. Onew was awarded the Newcomer Scene Stealer Award at the 2016 Scene Stealer Festival for his role in Descendants of the Sun. Onew was also confirmed for a new tvN program Eat, Sleep, Eat which serves local recipes through Southeast Asia. On August 12, Onew and Lee Jin-ah released a duet, "Starry Night", as part of SM Station, a digital music project by SM Entertainment. It is a pop jazz song which is the work of numerous artists, including Andreas Oberg, a Swedish guitarist and songwriter, and singer-composer Yoo Hee-yeol.
In October 2016, Onew wrote the song "So Amazing" for Shinee's fifth Korean studio album 1 of 1, and another song, "Beautiful Life", for its repackaged album, 1 and 1.
In May 2017, Onew and indie duo Rocoberry released the song "Lullaby" as part of SM Station. In June 2017, Onew was featured in Heize's music video for the song "I Don't Know You". In August 2017, shortly before the release of Age of Youth 2, Onew was accused of sexual harassment and decided to leave the project after discussions with the production staff of the show. Onew went into hiatus and did not participate in the remaining shows of Shinee's 2017 concert tour in Japan. On April 6, 2018, after eight months of investigation, the prosecution dropped all charges against him.
