In 2020, Hwasa debuted as part of the Refund Sisters with the single "Don't Touch Me," which reached number one in South Korea.

The stage name "Hwa Sa" (화사) is derived from the adjective "화사하다" (hwasahada), which means "to shine brightly".

[8] In March 2018, Hwasa released her second solo song, "Be Calm", as part of Mamamoo's sixth EP, Yellow Flower.

In April 2018, Hwasa joined the cast of KBS reality television show Hyena on the Keyboard; the appearance spawned a collaboration with rapper Loco titled "Don't".

Hwasa took part in writing and composing the song, and it topped the South Korean's Gaon Digital Chart.

[12][13] In February 2019, Hwasa made her debut as a solo artist with the digital single, "Twit," which she participated in writing and composing.

[15] "Twit" also peaked at number three on Billboard World Digital Song Sales chart for the week of March 2, 2019.

[16] Hwasa released the single "In The Fall," a collaboration with South Korean hip-hop producer Woogie, in October.

[27][28] Lead single "María" was composed by Hwasa and producer Park Woo-sang with the goal of showing her growth as a singer-songwriter.

[32] On season six of JTBC's entertainment show Hidden Singer, Hwasa was one of the contestants for the episode airing on September 11, 2020.

[47][48] In March 2023, it was revealed that Hwasa would be a part of Dancing Queens on the Road, a twelve-episode television variety show aired on TvN, along with Kim Wan-sun, Uhm Jung-hwa, Lee Hyori and BoA.

[52][53] On October 4, Hwasa released "Chili", a digital single for the Mnet show Street Woman Fighter 2.

[55] In May 2023, the Student and Parent Human Rights Protection Coalition of Sungkyunkwan University filed a police report against Hwasa for public indecency due to racy and sexually suggestive dance moves, including licking her fingers and touching her crotch, performed at the public festival.

Shin Min-hyang, representative of the Coalition, filed the police report stating "Hwasa's controversial stage for obscenity was seen not only by students, but also by parents and the general public, so an unspecified number of people felt uncomfortable."

The police stated that "after investigating the content of the performance, and comprehensively reviewing the statements of those involved, it was determined that it would be difficult to bring up criminal charges [with the presented evidence].

[61] Also, she was ranked 9th in annual survey for Gallup Korea's Singer of the Year in 2020 under the category selected by respondents in age group 13 to 39.

[62][63] She also has been placed first occasionally on the Korean Business Research Institute's monthly "Individual Girl Group Members Brand Power Ranking".

[75] In November, she teamed up with Vogue magazine and Urban Decay cosmetics for their "Pretty Different" and "Queen" inspired concepts.

EA Korea released "Play With Life", a Sims 4 commercial film video featuring Hwasa.

[81][82] Hwasa later on became Kiss New York's new muse in April,[83] and the following month, she was chosen as a model for a hangover drink by Lotte Chilsung Beverage.