The I'Park jumped out to an early lead, when Han Ji-ho scored in the 30th minute, on a helper from Park Jong-woo.
They increased their lead by two in the second half when Kim Han-yoon scored in the 54th minute, though Sangju mounted a late charge when Kim Chi-woo scored in extra time to break Lee Beum-young's shutout.
The I'Park are suddenly undeafeted in their past four games, though they still have yet to win a regular season game. They now have two wins and a loss in Rush Cash Cup action.
By Jeff Liebsch