Kim Yui was thought to be a sweet, caring and thoughtful girl who didn't judge people by their looks. Because of this false impression, Hyung Suk fell in love with her. But in his old body, Hyung Suk was greatly insulted by Kim Yui because of his appearance. It was also shown that Kim Yui was a dishonest person since she cheated on her boyfriend while stating that she didn't. After seeing her true colours, Hyung Suk stopped having a crush on her.
Currently, Kim Yui is more polite and respectful, only sometimes acting harsh whenever she finds someone else 'stealing' Jin Sung. She is also aware of what she had done wrong in the past and she's grateful towards Jin Sung, now in love with him.
Kim Yui was introduced to be one of the top streamers by Pyun Duk Hwa. After watching Hyung Suk and Pyun Duk Hwa perform, she meets Hyung Suk (in his new body) in class and starts flirting with him, stating that his performance was great. After that, Kim Yui starts being exceedingly generous to Hyung Suk, even offering him a wallet of an expensive brand. Startled at such a gift, Hyung Suk rejects the present, stating that it is too much. Kim YuI then seduces him with a flirty yet innocent look in her eyes. Hyung Suk blushes and realises that she may be interested in him. From then on, he starts to have a crush on her.
During class, Park Ha Neul asks her friends if they want to go to karaoke. While everyone else in the group agrees to go, Kim Yui states that she would prefer to go shopping. Everyone instantly changes their mind and decides to go shopping instead. When they all go shopping, Park Ha Neul brings out a light blue pouch with a picture of a doll and asks if she should buy it. Everyone else turns to Kim Yui to wait for her opinion and she says that it looks ugly and that it doesn't suit her. Everyone else immediately agrees, which Park Ha Neul all sullen.
Next morning, Park Ha Neul sees that Kim Yui has the exact same pouch and gets confused by that fact that she called it ugly and then proceeded to buy it. When she tries to confront Kim Yui about it, Kim Yui and her friends ignore her and pretend that she didn't even say anything. Hyung Suk enters the room and Park Ha Neul becomes delighted, but then she sees Kim Yui flirt with him, with him shyly flirting back.
Later that night, Kim Yui continues broadcasting, acting all innocent and cute. She watches as some viewers were competing to see who could pay her more and she smiles sadistically. Kim Yui then talks about how she started playing 'Heroes of the Storm' and asks her viewers if they want to challenge her in the game. A while after all the broadcasting had ended, Kim Yui starts to take out a cigarette and smoke, just before a boy uncovers himself from under the blankets. He gets agitated and asks how long they are going to keep their relationship a secret, and Kim Yui calls him a 'goof'.
She then proceeds to smile innocently while stating that people won't give her any balloons if they find out that she has a boyfriend and gives her boyfriend the wallet which she tried to give Hyung Suk. Thrilled at such an expensive gift, Kim Yui's boyfriend says that he can suck it up. Kim Yui gets on top of him and acts all sweet and caring, only to think that he's a bore and she then starts to wonder what Hyung Suk is up to.
Hyung Suk, wanting to make sure that she'll accept his old body, asks Kim Yui of what she thinks of fat people. She states that 'people are still people' and Hyung Suk gets pleased at her response. He then thinks of her as 'innocent', 'sweet' and 'different from the other girls' while Kim Yui smiles at him sweetly. Kim Yui then proceeds to smile wickedly at Park Ha Heul in a sinister way while Park Ha Heul watches them in misery.
While Hyung Suk, Pyun Duk Hwa and Park Ji Ho hang out together, Kim Hui sits in front of her computer in anger as she stares at how high Park Ha Neul's rankings have become. Desperately wanting to be better than Park Ha Neul, Kim Yui tries to act cute and innocent by saying that she 'poo-pooed', only to realise that just sounds weird. Even then, people give her balloons because they think she's cute and Kim Yui sits there, gladdened, stating that pretty people get paid, no matter what.
Afterwards, Kim Yui and her boyfriend go to the shop which the old body of Hyung Suk works at and Hyung Suk gets thrilled to see Kim Yuu there and thinks that her boyfriend is actually just her brother. When Kim Yuk and her boyfriend bring a pack of condoms to counter, Hyung Suk gets confused and asks himself why siblings would want to buy such an adult product together. Kim Yuk notices him staring at the box and asks if he's ever seen those before and calls him a pig.
He then sees that Kim Yui's acting rude and he gazes at her in confusion, not saying anything. Her boyfriend, noticing him gazing at her, orders him to lower his eyes and says that he knows what Hyung Suk is thinking when he looks at her. Kim Yui glares at Hyung Suk and coldly muttered that he makes her sick, which shows even more of her true colours. Hyung Suk then gets reminded of how kind Kim Yui acted towards him in his new body, not realising that he was still gawking at her. She then tells her boyfriend that she thinks he's a pervert and her boyfriend immediately swings his arm at Hyung Suk, only to have Hyung Suk dodge it — to everyone's surprise. Getting embarrassed that he missed, Kim Yui's boyfriend tries to punch Hyung Suk again, only to be stopped by Jin Sung. Jin Sung calmly asks Kim Yui's boyfriend to not hit Hyung Suk, since he owes Hyung Suk something. Kim Yui's boyfriend, annoyed by this statement, goes towards Jin Sung to fight, calling him 'arrogant' and 'a disrespectful kid'.
Jin Sung notices the expensive branded wallet in Kim Yui's boyfriend's hand, which Kim YuI first tried to give to Hyung Suk, and Jin Sung states that she's nervy. He asks in surprise that she had a boyfriend all along and her boyfriend stares at him in confusion, not knowing what was going on. Jin Sung then informs that she tried to give it to Hyung Suk but he refused it, and Kim Yui gets shocked. Kim Yui, not wanting her boyfriend to know, says that he's lying and pleads to her boyfriend so then that they could leave. Kim Yui's boyfriend, interested, stops Kim Yui and asks Jin Sung to go on. To Kim Yui's horror, Jin Sung explains that Kim Yui secretly loves a 'pretty boy' in her class and likes to give him presents, and that the 'pretty boy' likes her too. After going on about how she loves him and tries to get his attention, Kim Yui's boyfriend rages and punches Kim Yui in the nose, making it bleed. He continued to kick her body while she's on the ground and step on her head, and this shocks and angers Jin Sung. He walks towards Kim Yui's boyfriend and says that he shouldn't hit a girl. This annoys her boyfriend and he tries to harm Jin Sung, even though Jin Sung kept punching him back. After finally beating Kim Yui's boyfriend with his own two hands, Jin Sung states that 'you should not hit a flower, even if it's with a girl' even though it's actually meant to be 'you should not hit a girl, even if it's with a flower'. Right then, Kim Yui becomes grateful towards Jin Sung and falls in love with him.