Jin Bo Ra, later legally changed to Jin Seo Yun and known professionally as Sunday, is a South Korean singer, dancer, musical actress, and member of THE GRACE (천상지희 더 그레이스).

She made her debut as a solo artist in July 2004 in Japan with the release of the digital single "Lila's Unrequited Love". The following year, she released a second digital single before eventually returning to South Korea.

She re-debuted in April 2005 as THE GRACE's lead vocalist with their first single, "Too Good". The group was formed by SM Entertainment (SM엔터테인먼트) as the female counterpart to TVXQ and managed to successfully debut in South Korea. Their performances were picked up by Japanese and Chinese TV stations, and they recorded all their singles in Japanese and Mandarin before officially debuting there in January and March 2006, respectively.

But, after successful tours around Asia and more releases in different languages, the group went on an indefinite hiatus in May 2010. She joined member Dana and performed as a sub-unit DANA & SUNDAY (천상지희 다나&선데이) in 2011, releasing only one single, "One More Chance", before also going on hiatus. They have never officially disbanded, but all members are now focused on their individual activities.

She left SM in 2021 after 16 years with the company and is now without representation and back in musical theater.

(Source: MyDramaList) Edit Biography