Rain (who was then known as Sun) began his career as a progamer quite late in the Brood War era, playing his first official match in April 2009 in individual league preliminaries. According to him, becoming a progamer was never his intention, as he just played casually (instead of studying) and participated in some tournaments, until he was recruited as a professional player by MBCGame HERO. Rain never managed to qualify for either the OnGameNet Starleague or the MBCGame StarCraft League throughout his Brood War career, only appearing in a few minor individual leagues. He realised noteworthy results in Proleague though, achieving a good 15-9 record in the 2010-2011 Shinhan Bank Proleague for team SK Telecom T1. His crowning achievement took place in the STX Masters 2011, as he managed to all-kill Hwaseung OZ in the finals (defeating sHy, Jaedong, Killer, and HiyA).
Rain played his first official StarCraft II match on May 20, 2012, in the opening match of the hybrid 2011-2012 Proleague Season 2, as SK Telecom T1 faced Team 8. He defeated Jaedong in this encounter, and went on to appear in the majority of the matches played by SK Telecom T1 in the league, being used as the team’s ace player. On July 19th, Rain attended the 2012 OSL Season 1 preliminaries; the first season of the prestigious league dedicated to StarCraft II, and successfully earned a spot in the tournament, a feat he had never achieved during his short career as a Brood War progamer. A few days later, he qualified for the OSL main event after placing second in his group in the KeSPA player’s dual tournament, hence making it to the main tournament. After these matches, he expressed his delight of getting to play on stage for the OSL final rounds, which he described as being his longtime dream.
Rain found more success in individual leagues in early September 2012, as he cemented his reputation as the best KeSPA player at the time by advancing in both the OSL Season 1 and the GSL Season 4 Code S. In the latter tournament, he placed second in his round of 32 group. Rain delivered an impressive performance in the OSL round of 16, topping a group in which he was the underdog with three victories over the StarCraft II veterans DongRaeGu and MarineKing and over the reigning, double OSL champion (in Brood War) JangBi. The Protoss player indeed emerged on top of his GSL round of 16 group as he defeated TaeJa and Polt, both renowned for their mastery of the Terran-versus-Protoss match-up.
On March 15 2013, Rain would play in his first Heart of the Swarm tournament which was 2013 MLG Winter Championship, he qualified for this tournament back in February. In the Round of 8, his opponent was none other than INnoVation who defeated Rain in the past but Rain has also taken games off of him so it should have been a close match but it was not, INnoVation 3-0′ed Rain and knocked him out of the tournament. Rain did not participate in the 2013 WCS Season 1 Korea GSL Up & Down’s like he was supposed to as he was seeded into Code S. After being knocked out, Rain played in the 2013 WCS Season 1 Korea GSL Challenger League, he was placed into the Round of 32 he was able to defeat his 2 opponents allowing him to advance into Code S for the next season.
On February 5 2014, Rain started his journey in Code S. Despite losing his first series, he was able to move on into the Round of 16.
After that, Rain travelled to Cologne, to participate in IEM Cologne. He got there by winning Korean and Taiwan Qualifier. Then at the Asian Final Qualifier, he won his first two matchups, losing the third. Dropping down to the lower bracket, he ultimately was able to advance into Stage 2 of the main event in Cologne. There, he was placed into group of heavy fan favourites HerO, ForGG and HyuN, but he was able to top group with 4-1 score and moved into Ro8. Rain advanced into the Ro4, where he ultimately lost to Polt in a back and forth series (3-2 in favor of Polt) and finished tournament in 3rd-4th place.
After coming back to Korea, Rain played in all-Protoss Ro16 GSL Code S group, with Squirtle and two SK Telecom T1 teammates. Rain was able to win against both SKT T1 mates and went into Ro8 where he met herO again, who just lost finals of IEM World Championship to sOs. Rain won 3-2 and advanced into semifinals. In Ro4, he met Zest who was going strong, knocking out SKT1 players in every league he played since his all-kill of SKT T1 in Round 1 of Proleague. Rain was toppled 2-4 and finished in 3rd-4th place.
The next season of Code S was Rain’s fourth consecutive appearance in Code S, if not counting OSL. In the Ro32, he won his group with 4-1 score. However, in the Ro16, Rain lost to Solar and Life and with a 1-4 score, fell into Code A.
He was placed in Group D for GSL S3 Code A placing first in his group with the map score of 4-0, thus lifting himself back up to Code S. Rain then cruised through his Code S group, beating the GSL Season 1 Champion, Zest and Rogue. He had a similar run on his Ro16 group cruising over EffOrt and Solar. However, on the Ro8, Rain was matched up against Zest and was beaten 0-3.
On September 11, 2014 (during his Code S run), he announced that he declined to re-sign a new contract with the team SK Telecom T1 and expressed his desire to play in a non-Korean team. He officially left the team on September 30.
He played in the 2014 KeSPA Cup that took place from 11 to 14 September. He qualified into the Ro16 but was knocked out by Bomber 1-3.
He was able to get a seed into the 2014 Hot6ix Cup by advancing through the Online Qualifiers. In that run he was able to advance to the semi-finals of group A. In the group stage, he advanced in Second place. It was then announced that Rain will not play in the Round of 8 because he choose to go to IEM San Jose instead. His spot will be taken by PartinG, the winner of a wildcard group.
On November 10, 2014, it was announced that he had joined mYinsanity.
During the first half of 2015, Rain took advantage of being in a foreign team by travelling from continent to continent to attend tournaments. He travelled abroad more times at the first half of 2015 compared to the whole of 2014.
Rain started 2015 by topping his Ro32 Group in the GSL 2015 Season 1, dispatching Panic and the 2014 Blizzcon Champion Life. With more than a month between his Ro32 and Ro16 matches, Rain had time to attend a foreign tournament in the form of IEM Taipei.
Returning to Korea to play his Ro16 matches for GSL, he was pitted against two Zergs and a Terran. However, his run ending on February 25 meant that he had a great amount of tournament-free time before his GSL S2 Code A matches.
He then attended IEM World Championship in Katowice, his ticket being his second place finish in IEM San Jose. Rain’s run however was cut short by a 0-3 defeat in the hands of his former teammate FanTaSy.
Rain then attended another major offline tournament in Europe in the form of Copenhagen Games after cruising through the online qualifiers. He then went through Group Stage 2 and 3 in a similar fashion, having a perfect map score of 8-0 across the two stages. However his run was stopped by FanTaSy again in the semifinals after blowing his 2-0 lead to lose 2-3. Rain went home with $750 and 150 WCS points.
Rain also found some time to play in online cups and travel to offline foreign tournaments between his GSL matches such as the ASL Prime League bagging himself $2000. He also attended Dreamhack Tours in France, in which he achieved a top 8 finish after being beaten 0-3 by PartinG in the quarterfinals.
No more than four days after his GSL Championship win, he flew over to Germany to play in TaKe’s HomeStory Cup XI as one of the invited players. In the Ro32, he made quick work of his first two opponents, beating them both with a 2-0 score. Rain did not have a flawless Ro16 run.