Tottenham were 5-2 winners on the south coast with Kane also on the scoresheet, though the England star was more impressive with his set-up play.
He was the provider on each occasion as Son scored four despite only making two assists throughout the whole of the last Premier League campaign.
Tottenham had looked poor during the first half with Danny Ings giving Southampton the lead.
Though Spurs equalised through Son on the stroke of half-time before the South Korean put Jose Mourinho’s side into the lead just after the break.
Southampton’s high defensive line was regularly broken with Kane at the heart of the build-up again setting Son clear on two more occasions.
Kane got the goal his play deserved later on before Ings scored a late consolation from the penalty spot.
Four-goal hero Son said: “It’s incredible to score four goals in the Premier League.
“Obviously without team-mates and Harry Kane’s passing, I wouldn’t have scored that many goals. Three points is the most important thing. I’m happy to score four but more happy with the win.
“Finishing is probably what I say is my main skill and it was not even difficult finishing because Harry’s passing was incredible. That is the first time I have scored four goals in my life.
“I’m very happy that Harry Kane scored. When you make an incredible game with four assists, he’s one of the best strikers in the world, he’s hungry. I’m very happy he scored today.
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“Harry is the man of the match. He scored a goal and had four assists. We’ve been working together so long so we know each other. We work really hard.”
While Kane himself added: "We spoke before the game that there would be space in behind.
“There was one pass [to Heung-min Son] where I didn't even look. It was just about putting the ball in the spaces.
"It's a connection we've been building for some time now, I'm proud of him."