A second-half penalty from Andreas Granqvist gave Janne Andersson's side all three points and sent them joint-top of Group F with Mexico, who beat defending champions Germany a day earlier.
Clear-cut chances were few and far between but Sweden were good value for their victory, with South Korea failing to muster a shot on target.
Shin blamed much of the loss on the fact his players could not match their opponents physically, even though each side managed two headed shots in the match.
"The Swedish players are very tall. We prepared to play against tall players and, rather than contact, we focused on height," he explained.
"After the first half we felt we would adjust and that in the second half we would be able to find chances. They did adjust very well; it's a pity they gave away a penalty.
"Among the 32 teams, I think they [Sweden] are tallest or one of the top two. They will be a real threat because of their height."
Granqvist scored from the spot after a lengthy VAR review, with referee Joel Aguilar initially deciding Kim Min-woo had not fouled Viktor Claesson.
Shin was frustrated to concede the penalty but accepted the right decision was eventually made.
"I think we have to follow what the referee decides," he said. "Of course we could say it's regrettable, but he [Claesson] was caught.
"We agree that it was a good call."
A defeat against Mexico in their second match on Sunday (AEST) could see South Korea's exit from the tournament confirmed, and Shin expects a difficult test.
"They were very fast, very skilled, they're a tough team so they are going to be a formidable opponent but we're going to look over the match with Germany, analyse it and find our way to deal with the Mexico team," he added.
