Kim destroyed co-medalist Mina Harigae 9 and 7 in Saturday's quarterfinal, then dispatched Tiffany Chudy, who bested Ya Ni Tseng 3 and 2 in the quarters, 4 and 3.
Joh beat Maria Jose Uribe, 3 and 2 in the quarterfinal round and handled Sara Brown, who topped Angela Oh 4 and 3 Saturday morning, 3 and 2 in the second semifinal match.
Saturday's action got off to a rocky start as there was a weather delay that lasted almost two hours.
In the semifinals, Kim, a 14-year-old from Hawaii, wasted little time in building an advantage in the semifinals against Chudy. Kim won four holes in a row from the second and by the time they made the turn, she was 4-up.
Kim took the 11th hole with a par to move 5-up with seven to play. Chudy fought back to win the par-5 13th with birdie, but when the pair halved the 15th with birdies, Kim earned her spot in Sunday's 36-hole final.
Joh won the second hole with a birdie and went 2-up with a birdie at the par-3 sixth. Her lead over Brown never grew to anything higher than 2-up, but Brown was unable to make a significant move.
Brown took the par-3 12th with a birdie to cut the gap to 1-down, but bogeyed the 13th to fall back to 2-down. Joh won the 15th with a birdie to go 3-up with three to play.
They halved the 16th with bogeys to set up Joh's match against Kim on Sunday.