[4] Han travelled to Barcelona that autumn, where he trained at the Marcet Academy (also known as Centro Europeo de Tecnofutbol).

During his brief time in Spain, Han and his teammates underwent training, fostering their mentality and honing their talents before their participation in the AFC U-16 Championships in Thailand.

[2] It was not until 2017, as Han turned 18, when reported interests and offer from multiple European clubs including Liverpool and Manchester City came in.

[2] Sticking with the Italian roots, Han accepted an eight-week trial offer from Cagliari after being advised of his decision from his agent, Sandro Stemperini, and ISM Academy's sport director, Stefano Capozucca.

[7][9] On 10 March 2017, Han Kwang-song signed a contract with Cagliari on youth terms, joining their Primavera squad in the process.

[11] Additionally, Han became the second North Korean player to join a Serie A club, following in the footsteps of Choe Song-hyok who had signed with Fiorentina the year before.

[5][13] On his first day after arriving at Cagliari, he scored a hat-trick in a friendly training match, impressing the coaching staff who decided to promote him to the first team.

[16][17] His impressive start in the first team led to a renewal just four days later, earning his first professional contract with Cagliari until 2022, that was set to commence on 1 July 2017.

[24] On 2 September 2019, Han secured a deadline day move to Juventus on a two-year loan from Cagliari, with an obligation to purchase at the end of the term.

[36][37] He made his debut for Al-Duhail in the Qatar Cup semi-finals on 10 January, in a 2–0 win over Al-Sailiya, coming on as a substitute for Edmilson Junior in the 83rd minute.

[40] Han's first goals for Al-Duhail came on 6 February, scoring a brace against Muaither in the Emir of Qatar Cup quarter-finals; his side won 4–0.

[45] On 19 March 2024, the Japanese newspaper Choson Sinbo revealed that Han was playing at DPRK Premier League club April 25.

It was once alleged that most of his salary was sent to the government, but Han had signed a contract at his last club preventing him from sending any money to North Korea.