Yui Kobayashi  On August 21, 2015, Kobayashi along with 22 other members were announced for the newly created idol group, Toriizaka46 (now Keyakizaka46). Kobayashi made her musical debut with Keyakizaka46's first single, Silent Majority. In October of the same year, Kobayashi made her runway debut at the GirlsAward 2016 Autumn/Winter fashion show. As of 2019, Kobayashi has made an appearance in all Keyakizaka46 singles. She formed a duo named with Yui Imaizumi, first appearing in "Silent Majority" with the song "Shibugakawa". With Imaizumi's graduation in 2018, Kobayashi and Mizuho Habu formed another duo named , appearing in "Ambivalent" with "302-Goshitsu". She held performance center roles typically held by Yurina Hirate when Hirate was unavailable, including the 60th Japan Record Awards and the 69th NHK "Kōhaku Uta Gassen". Kobayashi is an exclusive model with fashion magazine "with" since 27 July 2018.. Additionally, on 13 March 2019, she released a photo-book titled , published by Kadokawa.