What's Wrong with Secretary Kim S01E09 - Let's Make it Official

Young-Joon is so happy that Kim Mi-So is now his girlfriend, he does not shy from showing that to anyone, and even going as far as doing some of her secretarial things instead asking her for it, which makes people at work puzzled. Park Yoo-Sik is rattled when he sees his ex-wife crossing the street with another guy in a friendly manner, for whom he assumes to be her new boyfriend or a lover. Ji-Ah and Gwi-Nam are becoming more friendly. Young-Joon hides in a closet when Mi-So's sisters come to visit her. Mi-So definitively tells Sung-Yun she's not interested in him, and also starts suspecting that Young-Joon may be the boy from her past after talking to his mother.