A pacey and prolific forward, Lee joined Ulsan ahead of the 2012 campaign with AFC Champions League football again on the agenda after helping Gamba Osaka reach the Round of 16 last year.
He had initially moved to Japan in 2009 to join Jubilo Iwata before returning to Korea after spending three seasons in the J.League.
And having scored twice for Gamba in 2011, Lee has started every game for Ulsan during this campaign and netted on four occasions - with two of those coming in the wins over Saudi Arabia's Al Hilal and Uzbekistan's Bunyodkor in the knockout stage which have left Kim Ho-gon's side within touching distance of becoming the third K-League side in four years to win the AFC Champions League title.
Lee was particularly effective in the 3-1 semi-final first leg win over Bunyodkor in Tashkent at the end of October with his endless movement and tireless running, the Uzbeks struggled to contain the bleached blonde 27-year-old as he switched between left and right while offering himself as a third striker alongside Rafinha and Kim Shin-wook.
This attacking philosophy, which saw Lee finish as the third highest scorer in the J.League last year, was born during his first spell in Korea with Daegu Citizen after cutting his teeth in the reserves of his hometown club Incheon United.
He was named the Best Player in the R-League, the Korean reserve league, while playing for Incheon in 2006 before joining Daegu under Byun Byung-joo at the beginning of the following season.
"At Incheon I just had to train and train with the hope that I would be a player with the team. I just had to train," said Lee.
"Then at Daegu the coach had an attacking mentality and he let me play as I want when attacking.
"The coach from Daegu has played a big part in my career and helped me progress a lot."
Lee's consistent return of goals at Daegu quickly established him as a fans' favourite, but with that came interest from overseas.
His contract with Daegu expired in December 2008 with English Premier League side Blackburn Rovers and Paris St Germain linked with the striker in 2009, although a move to Europe did not materialise and Lee opted instead to switch to Japan, first with Jubilo and then Gamba.
"Korean football focuses on speed and power but in Japan they are very sensitive and they concentrate on progressing the game. This helped me expand my game and I learnt a lot," added Lee.
"There were opportunities to move to Europe, but the timing was not ideal and I had to also consider the army."
Prior to returning to Korea, Lee scored a total of 32 goals in 88 league appearances during his time in Japan, with his 15 goals last season for Gamba making him the joint third highest scorer in the J.League.
In the AFC Champions League this season, Lee started every game as Ulsan won their group ahead of Japan's FC Tokyo before he crucially netted his first goal of the continental campaign with two minutes remaining in the Round of 16 against J.League champions Kashiwa Reysol to secure a 3-2 win.
Having fired home from the edge of the area to ensure Ulsan's progress to the knockout stage of the AFC Champions League for first time since 2006 - when they reached the semi-finals - Lee then showed his all-round ability with headers in the wins over Al Hilal and Bunyodkor.
With Ulsan seeking to defend a slender one-goal advantage against Al Hilal, Lee's back post header sealed Ulsan's empathic 4-0 win in Riyadh and a 5-0 victory on aggregate.
And his stylish flicked header in the first leg of the semi-final against Bunyodkor also wrapped up the scoring in Tashkent having earlier shown excellent vision to set-up Rafinha to level the contest in the first half as Ulsan went on to record a 3-1 comeback win.
And in the return fixture on home soil, Lee emphatically sealed Ulsan's 2-0 second leg win with an eye-catching first time strike which took his AFC Champions League tally to four in his last five games in the competition.
Having become the fourth successive K-League side to reach the AFC Champions League final, Ulsan are looking to follow in the footsteps on 2009 champions Pohang Steelers and 2010 winner Seongnam Ilhwa Chunma.
And with Lee's Korea Republic international team-mate Kim Shin-wook having netted six goals in the competition this season and Brazilian striker Rafinha scoring four goals in his last four continental outings, Ulsan will be confident of avoiding the fate of fellow K-League side Jeonbuk Hyundai Motors, who lost last year's final on penalties to Qatar's Al Sadd despite playing at home.