The move, confirmed by reigning K League 1 champions Jeonbuk on Tuesday afternoon, sees them continue a busy mid-season of adding reinforcements to their squad.
Jeonbuk have won K League 1 in the past four seasons but currently face a real fight to retain their crown in 2021, with Ulsan Hyundai currently holding a four-point lead over them at the summit having played a game more.
They are also still in the running in the ACL after advancing into the Round of 16 earlier this month, and the quest for glory on both fronts has arguably been a factor behind their hectic transfer activity.
Prior to Song's arrival, Jeonbuk had also secured the loan signing of Thai defender Sasalak Haiprakhon on loan from Buriram United, while Moon Seon-min -- who featured for Korea Republic at the 2018 FIFA World Cup -- also returned after returning a loan stint with Sangju Sangmu as part of his national service commitments.
But it is the signing of Song that is likely to get Jeonbuk fans most excited, given his status as one of South Korean football's most highly-rated prospects.
Still only 21, Song emerged as one of the K League 1's top attackers since making his professional debut with Pohang in 2018, and won the league's Young Player of the Year award last season.
The attacker, who primarily plays on the wing but can also feature in a more central attacking role, won his first senior cap for the Taegeuk Warriors earlier this year and scored in the recent 2022 World Cup qualifiers against Lebanon.
"He [Song] is a player who can play in all of the attacking positions, so I expect he will be able to help the team a lot," said Jeonbuk manager Kim Sang-sik, on the club's official website.
Song is currently on international duty with the Olympic team for the upcoming Tokyo Games and is said to have also been on the radar of several European clubs, although Jeonbuk ultimately won the race for his services.