Ji-soo has just been promoted from the B team to the senior squad.
The centre-half told the club's website: "First and foremost, I am truly honoured and grateful for the opportunity to train and play alongside such incredible players under the guidance of an exceptional coaching staff.
"I am excited to be moving in the right direction, and my parents are proud of me for taking this significant step forward in my career.
"I have worked on all aspects of my game this season, including fitting in culturally. When you move from another country, it is not easy to settle in quickly as you miss home, but I have remained determined to be the best I can in a new country and environment."
He added, "My goal has always been to make my Premier League debut as soon as possible, and I will continue to work tirelessly to achieve this objective.
"I am so excited and ready to be a positive impact on the team in any way that I can. I want to compete and I want to impress and I am ready to go. I am also excited to continue training and learning more about football under the guidance of Thomas Frank."