Core played with teammates SuDai, Beast, HuHi, and LinLan as the roster of Bigfile Miracle in HOT6iX Champions Summer 2014. Though the team had performed impressively in the Qualifier, sending Jin Air Falcons to the loser’s bracket, they went 0-6 in Champions, in a group with Samsung White, SK Telecom T1 S, and CJ Entus Frost. After Champions Summer, Bigfile released the roster.
On December 4th, 2014 it was announced that Core would be joining Team Dignitas as their starting AD carry under the name Core JJ for the 2015 season, replacing imaqtpie. In his debut, CoreJJ and Dignitas ended the Spring Split at 9th place. They then played in the Promotion Tournament and re-qualified for the Summer Split after beating Team Fusion. In Summer, they ranked 6th in the regular split and made it to the playoffs. However, CoreJJ and team lost to Team Impulse in the Quarterfinals and finished at 5th-6th place. The team also made it to IEM X Cologne where they finished 5th-6th, losing to Qiao Gu Reapers in the Quarterfinals.
After one season in NA, CoreJJ decided to go back to Korea. He then joined Samsung Galaxy for 2016 LCK Spring, as the team’s starting AD Carry]] and ended the split at 6th place. Although they did not make it to the playoffs, they were able to secure a spot for the team in the Summer Split.
Prior to the start of 2016 LCK Summer, Samsung announced that CoreJJ will be moving to Support position, as a substitute to Wraith. The team finished 4th in Summer Split and 4th in the playoffs, making it to the 2016 LCK Regional Qualifiers. Although CoreJJ has only played 3 games for the entirety of Summer, he played majority of their games in the Qualifies as well as in the 2016 World Championship where they finished at 2nd place after losing to SK Telecom T1. They also finished 1st in IEM XI Gyeonggi, thus qualifying them for IEM XI World Championship.
In the off season, Samsung announced that CoreJJ renewed his contract with the team and will continue to play alongside his 2016 teammates for the 2017 LCK Spring Split.