While plying his trade at Seongnam, he became the youngest player in the K League, South Korea’s top division, aged 17, and the first player in the league to sign a contract on semi-professional terms.
He competed in the 2023 U20 Asian Cup and 2023 U20 World Cup. South Korea reached the semi-final of the latter competition, beating France and Nigeria on their way before losing to Italy.
Ji-soo played in 19 K-League matches for Seongnam before his move to Brentford B in July 2023.
A month later he earned his first call-up to the senior South Korea squad, boss Jurgen Klinsmann selecting him for friendlies against Wales and Saudi Arabia.
The young defender was a consistent performer for Brentford B during the 2023/24 season, earning recognition from first-team head coach Thomas Frank who selected him on the bench eight times across the campaign.
Prior to the 2024/25 season, it was announced that Ji-soo would be promoted to Brentford’s first-team squad.
The centre-back made his Premier League debut coming on as a late substitute in a 0-0 draw with Brighton and Hove Albion in December 2024.
