Last week, Richarlison said he will seek psychological help on his return to England after the 26-year-old was photographed crying on the bench when he was substituted during Brazil's 5-1 thrashing of Bolivia in a 2026 World Cup qualifier in Belem.
Richarlison has scored five goals in 41 appearances for Spurs since joining from Everton in July last year and has been unable to nail down a starting place. His goal against Sheffield Untied on Saturday was his first in the league since April.
"It was tough for him and we all hoped that this game would help his confidence," Son said. "He changed the whole game. That's what we were waiting for.
"This is part of (being a) family," added Son, who also captains South Korea.
"I was probably more happy than him. We need him as a team; he has really good quality, but the confidence is massively different.
"Richy is a really strong guy, a good character and can always bounce back strong. But when you have a tough time you need good people around you."