Scheifele's three-point outing gives him five points in two games and a share of the playoff scoring lead along with four other skaters.
Rymarchuk's goal was the first post-season goal of his career in seven games.
Sam Bennett contributed with two assists in the loss.
Colts' goaltender Mathias Niederberger made 44 saves in the win. Mike Morrison picked up the loss for the Frontenacs after giving up five goals on 20 shots in 30 minutes of action. Colin Furlong replaced Morrison in the second period and stopped 11-of-13 shots in relief.
Barrie went 2 for 5 on the power play while Kingston scored four times on nine chances with the man advantage.
Ryan O'Connor, who led the Colts' defencemen in scoring during the regular season, received a game misconduct at 3:58 of the third period for a check-to-the-head infraction.
Game 3 is scheduled for Monday when the Frontenacs return home to host the Colts at the K-Rock Centre.
Elsewhere in the OHL, it was: Plymouth 3, Sarnia 2; Belleville 4, Mississauga 1 and Owen Sound 4, Sault Ste. Marie 2.
At Barrie, Ont., Camara and Theoret put the Colts ahead 2-0 just 1:17 into the first period, but Watsdon responded late in the period for Kingston to make it 2-1 after 20 minutes of play.
Vainonen tied the game 1:14 into the second period before Camara regained Barrie's lead just over two minutes later.
Scheifele and Athanasiou then scored 49 seconds apart to force Morrison out of Kingston's net and Rymarchuk made it 6-2 at 12:33.
Ikonen scored late in the second and Alcock opened the third period with another goal to make it 6-4, however Beyers added a late goal to put the game away.
Whalers 3 Sting 2
At Plymouth, Mich., Zach Lorentz and Mitchell Heard each had a goal and an assist and Alex Nedeljkovic stopped 25-of-27 shots as the Whalers edged Sarnia to take a 2-0 series lead.
Bulls 4 Steelheads 1
At Belleville, Ont., Tyler Graovac opened the scoring and then set up Jake Cardwell's third-period goal as the Bulls opened up a 2-0 series lead over Mississauga.
Attack 4 Greyhounds 2