She is currently active as a solo artist and actress, best known for her lead roles in the television series School 2017 (2017), The Uncanny Counter (2020–2023), and Business Proposal (2022).

Kim Se-jeong was born on August 28, 1996, in Gimje, North Jeolla Province, but moved to Anyang, Gyeonggi where she stayed with her mother and older brother at her aunt's house.

[10] They both made it to the final casting round along with contestants Nicole Curry and Lee Soo-kyung where Kim was eliminated from the competition.

Kim also collaborated with NCT's Doyoung on a song titled "Star Blossom" for the SM Station Season 2 music project.

[30] Kim and LEO were chosen to sing the official cheer song entitled "We, the Reds" for the South Korea national football team for the 2018 World Cup Tournament.

[34] In 2019, Kim took her second leading role in the mystery romantic-comedy drama I Wanna Hear Your Song where she played a timpanist who lost her memories due to traumatic events.

After a year of hiatus as a singer and three years since her solo debut song, Kim released the single "Tunnel" in collaboration with Dingo Music on December 2, 2019, followed by her first self-written and composed extended play titled Plant (Korean: 화분; RR: Hwabun), with its lead single of the same name, released on March 17, 2020.

[43] After two years of inactivity, on December 31, 2020, Jellyfish Entertainment disbanded Gugudan and on May 11, 2021, Kim renewed her contract with the company as a solo artist and actress.

[53] On July 23, 2021, Kim collaborated with Municon and released the digital single "Baby I Love U", a remake of the same song by Japanese singer TEE.

In February 2022, Kim starred as the female lead for the SBS romantic comedy Business Proposal alongside Ahn Hyo-seop.

[61] Kim also starred in another SBS television series Today's Webtoon alongside Choi Daniel and Nam Yoon-su that year.

[62] Kim's first solo fan meeting was scheduled to be held at Yes24 Live Hall on March 26, 2022,[63] but was later postponed to April 23, 2022, after she tested positive for COVID-19.

[67][68] Kim hosted the 2022 SBS Drama Awards with Business Proposal costar Ahn Hyo-seop and comedian Shin Dong-yup.

In 2020, she and her The Uncanny Counter cast mates, Yeom Hye-ran and Moon Suk, modeled for Dyson Coral hair straightener product.

[citation needed] In 2022, Kim was the endorser for cosmetic and clothing brands O!geti,[85] Julie's Choice,[86] and Roem; food and beverage products such as Goobne Chicken[87] and Lotte's Starlight Cheongha Sparkling Alcohol;[88] Living Workshop Household Goods[89] and popular video game Nexon's MapleStory where she was chosen to sing the theme song for Cygnus Knights.

[104] She appeared in other popular advertisements campaigns for various products such as Samsung's virtual assistant Bixby, Oella,[105] and GH Basic Housing.

[106] On March 8, 2022, Kim donated ₩10 million to the Hope Bridge Disaster Relief Association to help the victims of the massive wildfire that started in Uljin, Gyeongbuk and has spread to Samcheok, Gangwon.

[107] On March 31, Kim donated ₩10 million to Fruit of Love, Community Chest of Korea to help war refugees in Ukraine.

[108] On August 19, Kim donated ₩20 million to the Hope Bridge Korea Disaster Relief Association to help those affected by the 2022 South Korean floods.

[109] On September 7, Kim donated ₩10 million to the Hope Bridge Korea Disaster Relief Association to support those who suffered damages due to Typhoon Hinnamnor.

[110] On February 10, 2023, Kim donated ₩40 million to the Hope Bridge National Disaster Relief Association to help victims of the 2023 Turkey–Syria earthquake.

Kim cites IU, Girls' Generation's Taeyeon, and Ailee as her role models in singing and often uses their songs in her practice sessions.

"[120] Kim together with her group Gugudan are three-time gold medalists in three consecutive years and record holders for the Women's Archery Competition in Idol Star Athletics Championships and a gold medalist and record holder with her I.O.I and Gugudan member Mina in Women's Bowling Competition.