[9] According to Sawayama, the family's plan was to return to Japan when she turned ten, but they chose to stay in London.

While she began adjusting to her life in London, Sawayama attempted to "preserve" her Japanese culture by indulging in it which she said included listening to musical acts such as Hikaru Utada and Morning Musume.

Sawayama began her solo career in February 2013, with the single "Sleeping in Waking", produced by Justin "Hoost" Tailor.

[31] Sawayama described the genesis of the themes of the track as: "the digital world can offer vital support networks, voices of solidarity, refuge, escape.

"[31] In 2017, the singles "Alterlife" and "Tunnel Vision", a duet with Shamir, were released, followed by her debut EP, Rina.

[34] The Guardian deemed the EP "bracing and modern", stating that Sawayama had proven "she can shepherd pop into the future, too".

", a nu-metal, heavy metal, pop and avant-pop song, and "Comme des Garçons (Like the Boys)", a "homage to early 2000s dance tracks", both from her then-upcoming debut album.

[46][47] In June 2020, she released a cover of "Dance in the Dark" by Lady Gaga as part of Spotify's Singles series.

[52] Sawayama's movement gained major support from Elton John online,[53] who wrote that he was "happy to hear that the [BPI] are reviewing the rules that led to Rina Sawayama's well-deserved album being snubbed from this year's [Mercury Prize] list of nominees.

"[54][55] The British Phonographic Industry (BPI) later changed the rules to allow anyone who had remained in the UK, including her, to be eligible.

[56] On 26 October 2020, Sawayama made her television debut performing the song "XS" on The Tonight Show Starring Jimmy Fallon.

[59] In April 2021, Sawayama released an updated version of her song "Chosen Family", as a duet with Elton John.

[60] In August 2021, Sawayama was included on Newsweek Japan "100 Japanese people respected by the world" list.

[77] She has also starred in campaigns for Jourdan Dunn's Missguided,[78] and wrote and performed an original track titled "Play on Me" for Nicola Formichetti's MAC x Nicopanda.

[79] In September 2021, she walked the runway for Balmain to celebrate the ten-year anniversary of Olivier Rousteing being the head of the French House.

The genesis of the partnership was outlined in i-D.[82] Sawayama has said that she began singing after her family engaged heavily in karaoke and first sang "Automatic" by Hikaru Utada in front of her parents as its music video aired on television.

[84] She listed Aretha Franklin, Beyoncé, Janelle Monáe, Alicia Keys and Karen O as vocalists she admires.

At the age of twelve, Sawayama convinced her father to give her a guitar after she began listening to Avril Lavigne and taught herself to play chords on it.

[88] Other influences Sawayama cite include: Christina Aguilera,[89] Britney Spears, Evanescence, NSYNC, Kylie Minogue, Limp Bizkit,[90] Pink, Ringo Sheena and Taylor Swift, among others.

[93] Sawayama's incorporation of feminist themes is a recognition that, "pop music is a distinctly feminized genre and therefore, is imbued with the politics and positionality of women within a song or album’s respective moment in culture and history".

[100] In July 2020, she signed an open letter to the UK Equalities minister Liz Truss calling for a ban on all forms of LGBT+ conversion therapy.