[2] He holds a master's degree in international relations from University of California, San Diego.

[2] Following the graduation, he worked as a secretary for the ex-Prime Minister Lee Han-dong,[2][3] as well as an aide for a former MP Ryu Ji-young.

[8] The proposed amendment includes the prohibition of endorsing any political party or its candidates.

[8] On 15 July 2019, Yu and Paek Seung-joo, Liberty Korea MP for Gumi 1st constituency, submitted a motion to the National Assembly to dismiss the Minister of National Defence, Jeong Kyeong-doo.

[9] On 1 December, Yu's Bareunmirae membership was suspended, as a member of the dissident group, Emergency Action for Change and Innovation.