He was in charge of Son Heung-min, Hwang Hee-chan, etc.
Jang Ki-young, CEO of European professional soccer agent, says:
Soccer, Negotiation, the Soccer Industry, and How to Succeed as a Professional Soccer Player!

"The World of Agents" is a book about soccer from an agent's perspective.
CEO Jang Ki-young, who has worked as an agent for over 10 years, living half the year in the UK and half in Korea, generously shared what he has seen, heard, felt, and learned.
It contains various stories and specific information such as how to discover good players, how to send them to Europe, how transfer and salary negotiations proceed, what process is required to succeed as a professional soccer player, what kind of management is required, and what the future holds for the soccer industry.
In particular, as the author of this book, CEO Jang Ki-young, personally led Son Heung-min's transfer to Hamburg, transfers to Leverkusen and Tottenham, and salary negotiations in between, he not only reveals untold, dramatic stories, but also vividly conveys the transfer processes of representative Korean soccer players such as Hwang Hee-chan and Lee Dong-kyung.
This book will provide a unique entertainment experience and direct help not only to soccer fans who stay up all night watching European soccer, but also to young players and their families who are still sweating on the field, dreaming of playing for their national team or in European soccer leagues.

When we discover a player with the potential to advance to Europe, we first create a resume and related video about that player.
With that, the player analysts, including myself, comprehensively and holistically analyze almost every aspect of this player, such as his position, whether he is fast or strong, how old he is, whether he is a central midfielder or a winger, and whether he has experience playing for the senior team.
Once we've finished analyzing a player, we analyze whether he'd be a good fit for the Spanish league, the English league, or the German league. Then, we go into more detail and figure out which team would be the best fit for him.

--- From "Agent's Daily Life"

As an agent, and even as a human being, Jang Ki-young's life cannot be discussed without mentioning Son Heung-min.
He was the start that led me to choose the path of becoming a football agent, and he was my first player.
Heung-Min Son has been my dream, my glory, and my honor for a long time.
I sometimes think about the time when he and I were looking at the same place and running towards it.
I look back now and say that those were young, hot, and beautiful days.

--- From "Signing Son Heung-min's First Contract"

Tiss had an expert's eye.
Whenever I was struggling with the constant testing and contract failures, Tiss told me not to give up.
“Heung-Min is definitely a player with potential and promise.
The club also sees it similarly.
If I lacked the skills, I would have been the first to tell you to give up.
It's just that the timing isn't right right now.
So, if you wait a little while and keep knocking, the door of opportunity will definitely open.” These words of Tiss gave me strength, but I think they were also a great help to Heung-min.
Because the 'potential and possibility' spoken by a 'real expert' would have resonated much more deeply than my simple consolation of kindness and affection.

--- From "My Friend Tees Blymeister"

Daniel, who sensed that dragging it out any longer would only make things more and more unfavorable, called us first to finalize the negotiation.
When we asked for 300 million won per week, the response we got was that Harry Kane's weekly salary is 300 million won, and Sony doesn't have that much yet.
When I asked him what he would do, Daniel said he was thinking of a maximum weekly salary of 135 million won.
This only raises it by 50 percent, which is ridiculous.
We stopped negotiations, saying we would not renew the contract.
Of course, I had no intention of giving up on renewing the contract.
As I said before, an agent is someone who makes things happen.

--- From "Some Principles of Negotiation"

After that, Hee-chan scored a goal in his first game as a starter.
As I said before, the difference between a successful player and a unsuccessful player is this one point.
Of course, attack points cannot be increased solely through skill.
In many cases, luck and skill must be mixed together.
But there are players who somehow manage to make it happen when they have to.
Such players eventually become stars.
Just like Heung-min, Hee-chan did not miss the opportunity that came to him.
From this point on, Hee-chan began to play a full-fledged role, the coach began to trust him, the players became happy, and the famous Salzburg 'Ecstasy' trio was born.

--- From "The Club's Attitude to Acquire Players"

In 2018, Cheong Yong-i's contract with Crystal Palace was terminated without a specific destination being decided.
Personally, I found this situation very unfortunate.
We exchanged a few phone calls about this, and Cheongyong said that he would be happy to go anywhere, but only to Europe.
After much thought, I decided to explore the team with Tiss.
Looking at it that way, while most Germans are rather serious and rigid, Tiss is the warm and cheerful type, so he gets along well with Koreans.
When Cha Du-ri was in Germany, the two were quite close.
As he also had feelings for Cheongyong, Tiss promised to actively participate.
Just two days after putting their minds together, Tiss found a club that wanted Cheongyong.

--- From "Knock and Knock Again"