Episode 9 - S1.E9

Yi Soo wears the pink shoes given to her by Do Jin. He's happy when he sees her wearing them until he hears what he thinks it's her second false declaration of love, which hurts and upsets him. Because of this, he doesn't want to see her again. Once Yi Soo is back home, as the bubbles in her fantasy break like glass, she realizes she has fallen for Do Jin.