The People says Sir Alex Fergusonâ€™s scouts are camped out at Hamburg for the exciting young attacker, who could be sold for around ÂÂ£10million this summer.
And Rafa Benitezâ€™s Chelsea â€“ who would love an Asian idol in their squad â€“ are also keen on the youngster, whose Âdazzling skill and goals are being compared to ÂCristiano 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 â€“ and also appeal to the commercial side at Old Trafford.
Chelsea are even more aware of Sonâ€™s Âattraction in the Far East, where he could easily become the most significant Âplayer in the next Âdecade if he continues to improve.