Short answers, pulled from the story.
Yoasobi is a Japanese word meaning "nightlife." Ayase, who coined the name, described it as representing a wish to take on creative challenges after hours, with individual careers treated as daytime work and the Yoasobi project as what they did at night.
Yoasobi consists of Ayase, who writes and produces all music, and vocalist Ikura, whose full name is Lilas Ikuta. Ayase previously performed as vocalist for the rock band Davinci, while Ikura began her music career busking with a guitar at the age of 14 and later released solo EPs through an independent label.
Yoasobi formed in 2019 after Yohei Yashiro, founder of the creative writing platform Monogatary.com, proposed producing songs based on story submissions as a prize for writers. Ayase was recruited to produce, and he discovered Ikura through a cover video she posted on Instagram of Aimyon's song "Kimi wa Rock o Kikanai," contacting her directly afterward to propose the project.
Yoasobi releases songs exclusively based on specific pieces of fiction, whether submitted by the public to Monogatary.com or written by professional novelists and manga artists. Songs not grounded in a fictional story are released by the members under their individual names rather than as Yoasobi.
"Idol" spent 22 non-consecutive weeks at number one on the Billboard Japan Hot 100, surpassing the previous record of 13 weeks held by Official Hige Dandism's "Subtitle." It also became the first Japanese-language song to top the Billboard Global Excl. US chart and was certified diamond by the Recording Industry Association of Japan within 295 days of release, the fastest any song had reached that milestone.
"Yoru ni Kakeru" went viral during the COVID-19 pandemic in Japan in early 2020, aided by a solo home performance by Ikura that spread widely on social media, carrying the song from number 76 on the Billboard Japan Hot 100 in March to number one by May. It became the first single with no physical CD release to top Japan's year-end chart, and later earned both diamond and double diamond certifications from the Recording Industry Association of Japan, becoming the first song in Japanese music history to receive either distinction.