Si-eun leads Hye-in to meet another member of the Diamond Club - Lee Duk-Min. Despite being wealthy, Duk-Min's peculiar and shy personality makes the students think he's poor. Si-eun tells Hye-in that Duk-Min could lend her 80,000 won and asks her to text Duk-Min. As Hye-in moves away, Si-eun looks up at the honor board and sees her name under the black club, the only one behind the diamond club. Meanwhile, Duk-Min calls Hye-in to a room and agrees to pay her 50,000 won to take photos of her in suggestive lolita outfits. Hye-in hesitantly agrees, but just as she completes the task and is about to leave, Duk-Min offers an additional 30,000 won if she agrees to change into another outfit right in front of him. Hye-in feels scared, but for the money, she reluctantly agrees. Meanwhile, Do-eon visits Hae-in in the hospital and recalls their last conversation before her accident. At that time, Hae-in and Do-eon had argued because he tried to defend Hae-in from Je-na and his father. Hae-in asks him to leave her alone for some reason she still can't clearly explain. Do-eon goes to the school to check the CCTV footage from the night of Hae-in's accident but finds that the files are missing. He remembers Hye-in had seen the silhouette of a female student on the rooftop and thinks about which student could be responsible for the accident. Meanwhile, Woo-jin is having dinner with Yul-hee. They discuss celebrating their 5-year anniversary, but Woo-jin asks if they can have sex because Yul-hee wants to wait until they're married. Yul-hee says she's okay with being intimate but wants to wait until marriage, leaving Woo-jin reluctantly agreeing, though it's clear he's not happy. He receives a call and steps out to answer it. He screams because the caller mentioned something about Je-na discovering a lie he told Yul-hee.

The next morning, Hye-in wakes up from a nightmare about Hae-in's accident. She remembers how Hae-in grabbed a necklace from her attacker and gave it to Hye-in after falling from the building. Hye-in wakes up and checks her drawer for the necklace.

That day, Je-na sees her father's lover, also an English teacher, Ha, return to Cheongdam International High School to meet a colleague. Ha talks to her colleague, mentioning her engagement to a wealthy man. Je-na overhears and becomes anxious again.

Ms. Ha pretends to be kind to Je-na in front of her colleague, but once they're alone, she reveals that she's expecting a baby boy - the heir to Mr. Baek's empire, and she warns Je-na to behave. Je-na is shocked by her audacity.

As Ms. Ha continues to emotionally torment Je-na, Hye-in intervenes just in time and offers to take Je-na away. She asks Ms. Ha to leave them alone. Hye-in takes Je-na to a classroom and gives her water. However, Je-na still tries to appear tough and arrogant, stating that she doesn't need pity from someone like Hye-in. Hye-in, angered, throws the money for the dress into Je-na's face, revealing she knows Je-na is the one who pulled Na-yeon’s string để and got hye in into trouble this time.

She declares she won't leave the school and will persevere no matter what Je-na does to her. Hye-in tells Je-na that the scariest person in the world is actually Hye-in herself because she has nothing to lose.

The two girls finally come to a truce and decide to never cross paths. With newfound freedom, Hye-in finally starts focusing on her studies and keeps a low profile at school. However, Do-eon continues to pretend they are still dating. He takes Hye-in to the rooftop and tells her that her father is actually trying to cover up Hae-in's accident.

Do-eon asks for her help, but Hye-in doesn't want to get involved. She leaves him alone but suddenly receives an anonymous text. The text contains a video of her stripping in front of Duk-min, filmed from a hidden angle. Someone had installed a camera in the room to film Hye-in.

That day, Yul-hee and Je-na are shocked to see Si-eun with Hye-in. In class, Si-eun writes a note in Je-na's book, checking up on her.

Later that night, Hye-in is at home when she recalls the threatening note she had received at the mall. She compares the two notes and realizes they have the same handwriting.

Hye-in is shocked to finally learn that it was Si-eun who had been threatening her all along. Si-eun visits Hae-in in the hospital. When being left alone in the room, Si-eun tells the unconscious Hae-in that she is jealous of her because she was able to seduce Do-eon.

As she leaves the room, Si-eun laughs devilishly upon receiving the secretly filmed video of Hye-in stripping from Duk-min.