"How did he know?"
Hmm, maybe because you're not so great a Thespian as you think, Miss Choe.
And this ain't looking good… Jiyong's strategy to deal with Mr Bang and Soedol is bait and switch and putting some distance between the two first. But they're in a narrow corridor and I bet there's a localiser on Miryeo. Soedol will come from behind them, thus cornering Jiyong and nullifying his strategy.
Unless, of course, Gang-ok or Jo Heon show up in the last minute. Then again, there's no way Jiyong won't have thought that Miryeo has a tracker on her.