Hellas confirmed the transfer via the club's official website on Friday, bringing an end to Lee's six-year tenure at the Camp Nou, having joined Barca in 2011:
ESPN FC's Sam Marsden reported on the transfer and spoke of the comparisons drawn between Lee and Messi following his arrival in Catalonia, although he'll now look to realise that potential in Serie A.
Any progress made at the Camp Nou was halted by the transfer ban imposed on Barcelona in 2014 as a result of their infringement on rules against signing under-age players from abroad—of which Lee was one.
The South Korean was prevented from featuring for the club's youth teams until he turned 18—in January 2016— as a result.
Nevertheless, Lee was outlined by FIFA.com as one of the starlets to keep an eye on at this year's under-20 World Cup, per fan account La Masia:
Hellas are making their return to Italy's top flight after finishing second in Serie B last season, and the acquisition of Lee follows the much more experienced trio of additions made in Alessio Cerci and Martin Caceres.
Per Marsden's report, winger Lee scored 10 goals in 30 appearances for Barcelona's under-19 squad last season and will be hopeful of recreating those kind of numbers once again in Italy.