KyungSeok "Kasey" Yu is a South Korean tuba player recently appointed as Principal Tuba of the Incheon Philharmonic Orchestra in the spring of 2021. KyungSeok has performed in South Korea and international venues such as Seoul Art Center, Jordan Hall, Boston Symphony Hall, Weill Recital Hall at Carnegie, and Musikverein.

KyungSeok and his colleagues organized a brass quintet called Brass Arts Seoul in 2013. The team took second place at the 2013 Jeju International Brass and Percussion Competition affiliated with the World Federation of International Music Competitions (WFIMC). In 2015, the team made another leap in domestic music after winning the 2015 Artsylvia Chamber Music Audition, followed by three years of sponsorship and support in performance management. After earning such a reputation, the team was invited to the WFIMC Winner's concert, 2015 Seoul Spring Festival of Chamber Music, Jeju International Brass Festival Concerts, and four regular concerts held in Seoul.

KyungSeok has experience in performing as a Guest Principal Tuba with Suwon Philharmonic Orchestra in 2016 at Herrenchiemsse Festival in München and with the Boston Pops Orchestra in 2019. Moreover, KyungSeok performed with the Rodney Marsalis Philadelphia Big Brass for KCP Present Series in Vermont in 2018. In 2019, he participated in the Association of Performing Arts Professionals (APAP) Showcase in New York and their national tour held in Texas and Oklahoma.

KyungSeok graduated from New England Conservatory and holds his master's degree and performance diploma at Boston University studied with Mike Roylance and Ken Amis. He is currently in the doctoral program at Seoul National University.