Lee "PoohManDu" Jeong-hyeon (Hangul: 이정현) is a coach for SK Telecom T1
Lee "PoohManDu" Jeong-hyeon joined GSG in December of 2012 as their support under the name ManDu. The team played in OLYMPUS Champions Winter 2012-2013 but failed to make it through groups. ManDu left the team in February to join the new SK Telecom T1 2 roster that featured Piglet, Impact, bengi, and Faker. It was at this time that he changed his name to PoohManDu to match his lane partner, Piglet. The team's first tournament together was OLYMPUS Champions Spring 2013 where the team found immediate success. They placed third after losing 3-1 to MVP Ozone but they beat CJ Entus Frost 3-0 in the third place match. SKT1 2's sister team, SK Telecom T1 1 was dropped from the organization so Impact's team was renamed to just SK Telecom T1. Next, they attended HOT6iX Champions Summer 2013, this time managing to qualify for the finals. They were pitted against the KT Rolster Bullets and even went down 2-0 initially in the set but they managed to bring it back and win the tournament with a 3-2 victory. This win earned them enough circuit points to qualify for the Season 3 Korea Regional Finals. They were automatically seeded into the finals where they faced the Bullets once again, this time taking them down 3-1 to qualify for the Season 3 World Championship as the third seed from Korea. SKT went 7-1 in their group, only dropping a game to OMG and was put against the Gamania Bears in the quarterfinals. They quickly dispatched the bears 2-0 and then went onto play a close set against NaJin Black Sword that they eventually won 3-2. The finals saw SKT playing against the Chinese Royal Club. Royal was no match for SKT and the set ended with a quick 3-0 and the crowning of SK Telecom as the Season 3 World Champions. A month later, the team was renamed to SK Telecom T1 K.
SK Telecom continued their streak of domination at PANDORA.TV Champions Winter 2013-2014. In an unprecedented show of strength, SKT managed to sweep the entirety of the tournament, culminating in a 3-0 victory over Samsung Galaxy Ozone. This is widely considered to be the most impressive feat achieved by any team as OGN is thought to have the highest level of competition in League of Legends. However, HOT6iX Champions Spring 2014 began the steady decline of SKT K as a team. ManDu stepped down from the starting roster for health reasons and SKT brought in Casper to replace him. SKT were upset in the group stages by the KT Rolster Arrows and barely scraped through to playoffs. They then met Samsung Ozone in the quarterfinals and were swiftly beaten 3-1. ManDu was given his starting position back because of the overall poor play of the team. Due to having the most circuit points in Korea, they were invited to participate in All-Star Paris 2014. After winning 6 games in a row, they 3-0'd OMG to take the tournament without dropping a game. They came back to Korea for HOT6iX Champions Summer 2014 but fell in the quarterfinals again with a 3-1 loss to Samsung White. SKT was forced to play a tiebreaker against Samsung White to determine who would go to the 2014 Season World Championship as the second seed from Korea. White was too strong for SKT, quickly sweeping them 3-0. SKT was knocked into the finals of the gauntlet where they faced a red hot NaJin White Shield that took out the former World Champions 3-1. ManDu left the team in September and joined Invictus Gaming as a coach in December alongside Mafa.
ManDu's first tournament with the team was the 2015 Demacia Cup Spring Season where they made the finals but lost 3-0 to EDward Gaming. IG placed fifth in the 2015 LPL Spring Regular Season but placed third in the 2015 LPL Spring Playoffs after losing 3-0 to EDG in the semifinals but beating Snake eSports 3-1 in the third place match. In May of 2015 he moved to the LSPL to coach IG's second team Young Glory. YG played in the 2015 Demacia Cup Summer Season but lost 3-1 to Vici Gaming in the round of 16. YG topped their group in the 2015 LSPL Summer Season to make the playoffs of the 2015 LSPL Summer Playoffs. They dropped out in the second round after 2-0 losses to Hyper Youth Gaming and 2144 Danmu Gaming. They made it to the 2016 LPL Spring Season Promotion Tournament but they lost in the first round 3-2 to Royal Never Give Up.
On December 30th, ManDu rejoined SKT as a coach.