The People says Sir Alex Ferguson’s scouts are camped out at Hamburg for the exciting young attacker, who could be sold for around £10million this summer.
And Rafa Benitez’s Chelsea – who would love an Asian idol in their squad – are also keen on the youngster, whose dazzling skill and goals are being compared to Cristiano Ronaldo.
The tall 20-year-old has been a regular for the South Korean national side since his debut three seasons ago.
Fergie has sent the Old Trafford club's top scouts to watch Son recently and he could find a place in his squad – and also appeal to the commercial side at Old Trafford.
Chelsea are even more aware of Son’s attraction in the Far East, where he could easily become the most significant player in the next decade if he continues to improve.