The exciting South Korea international's hopes of completing the deal before the London Olympics had looked dead, however the Bluebirds are now close to making it official
The Wales-based outfit have been in pursuit of the 22-year-old Cerezo Osaka winger for the past few weeks and the club's chief executive Alan Whiteley revealed they were hoping to finalise a deal "within the next few days".
"We're hopeful we'll be able to close that within the next few days," Whiteley said according to BBC Sport. "We think we've made good progress on the negotiations.
"Like all these things you always hesitate to say too much until the ink is on the paper. Obviously there's work permit issues as well but I think we've made pretty good progress this week."
Kim, who has also previously had interest from Celtic and Borussia Dortmund, is currently focusing on Olympic duty with the Korean team.
The left-sided winger scored two goals and provided two assists for his country in last month's World Cup qualifiers against Qatar and Lebanon.