Jo "CoreJJ" Yong-in (Hangul: 조용인) is the support for KSV eSports.
Jo "CoreJJ" Yong-in joined Bigfile Miracle in February of 2014 as an AD carry under the name "Core". They competed in HOT6iX Champions Summer 2014 but they lost all six of their games and placed last in their group. The roster was released in September of that year to join Quvic E-Sports.
Core left Quvic to join Team Dignitas along with Gamsu in December 2014. It was here that he changed his name to "Core JJ". The first event that they attended with the team was IEM Season IX - Cologne, which Dignitas was invited to after Team Curse declined their invitation. They lost 2-0 in the second round to Gambit Gaming. Dignitas ended the 2015 NA LCS Spring Season with a 6-12 record in 9th place. They were forced to play against Team Fusion in the 2015 NA LCS Summer Promotion Tournament. Dignitas reverse swept Fusion on their way to requalifying for the 2015 NA LCS Summer Season. Despite being tied for first with a 7-2 record halfway through the summer season, the team struggled throughout the last half and finished sixth at 10-8. Dignitas was swept 3-0 by Team Impulse in the first round of the 2015 NA LCS Summer Playoffs.
CoreJJ left Dignitas in November to join Samsung Galaxy in December as their new AD carry.
During the 2016 LCK Spring Season, Samsung Galaxy went 10-8 in sets overall. CoreJJ split time with Stitch for the starter ADC position. After looking like they could clinch the fifth and final seed for the Spring Playoffs, Samsung Galaxy were unfortunately denied by the surging Afreeca Freecs, who beat them by the game score tiebreaker, giving Samsung sixth place for the split.
During the 2016 LCK Summer Split, CoreJJ moved to support to make room for rookie ADC Ruler. As a support, he only played in three games during the regular season - all losses. Nonetheless, they managed to take fourth place with a 12-6 series record, seeding them into the first round of the 2016 LCK Summer Playoffs. Though they summarily defeated the Afreeca Freecs in the first round, they were matched against KT Rolster, a team who they had never managed to beat post-S4 in the LCK era, and they were swept 3-0, giving them fourth place in the season. Their accumulated points gave them enough to qualify as the second seed in the 2016 Season Korea Regional Finals. In a rematch against the Afreeca Freecs, Samsung lost the first game before swapping out veteran support Wraith for CoreJJ. With this swap, Samsung managed to beat the Freecs 3-1, moving up to the finals in a rematch against KT Rolster. With CoreJJ, Samsung upset the heavy favorites 3-2, breaking a 19 game losing streak and giving them the third seed to worlds.
At the 2016 Season World Championship, Samsung were drawn into Group D along with NA's Team SoloMid, China's Royal Never Give Up, and Europe's Splyce.