The result of the monthly pyramid game is out, and Soo-ji is shocked to learn that she is now ranked C with 5 votes, while Ja-eun is ranked D with 2 votes. Meanwhile, Ji-ae becomes rank F with no votes for her. Soo-ji is relieved by the results, but Ja-eun worries about Ji-ae. Ji ae’s bestie, Seung-yi, betrays her and votes for another girl after being bullied by Da-yeon. Soo-ji wonders who the other 4 people who voted for her are, besides Ja-eun. Ji-ae tries to talk with Seung-yi about not voting for her, but she has already gone away with her new friend. Woo-yi asks Ha-rin what they should do now that Ja-eun has joined the game and she and Soo-ji are no longer rank F students. Ha-rin acts as if she doesn’t understand what Woo-yi is talking about and leaves the classroom. Outside, Soo-ji loses the motivation to break the pyramid game as she is now rank C and won't get bullied anymore; Ja-eun calls her a liar. Soo-ji tells Ja-eun that everyone just cares about themselves, and she would do the same. Soo-ji also meets Ha-rin, who congratulates her for getting out of rank F. Although Soo-ji still knows she is a psychopath, it’s not Soo-ji's priority now to fight against her. After that, she returns to the classroom. Everyone looks at her differently; from disrespect to intimidation. Da-yeon's group starts to bully Ji-ae, but Do-ah intervenes and tells them the ranking treatment is effective tomorrow, not today. Soo-ji again goes to the convenience store and buys an extra triangle kimbap to give back to Seung-hwa. When she pays, he notices the pyramid game app on her phone. At that moment, someone from the class starts to message Soo-ji, asking to be friends. Soo-ji, annoyed by how fake they are, curses out. Soo-ji is now added to the class group chat, and more girls try to befriend her, the same girls who mistreated and trash-talked about Soo-ji the other day. The next day, Soo-ji talks to them, pretending to forget what they did to her. They tell her that Ha-rin is not going to be in class because she is out on a trip with her family. Meanwhile, Ha-rin is at an orphanage. In the garden, Ha-rin burns a little girl's hand and threatens her not to tell anyone. Soon after, the child runs inside crying, and Ha-rin also comes in to join her family, who are giving gifts to the kids. Her grandmother, Mrs. Byun Cho Soon, tells Ha-rin that the little girl looked like Ha-rin when she was little. After her grandma's comment, Mr. Baek leaves the scene. Mrs. Byun expresses her pride in Ha-rin and asks her daughter-in-law to make sure Ha-rin gets whatever she wants, hoping she'll eventually take over the school. Meanwhile, after the vote, life at school for Soo-ji completely changes; she no longer has to endure bullies and receives respect from those ranked lower than her, which also makes her start acting cocky. One day in the bathroom, Ye-rim tells Soo-ji that she voted for her because she wanted to help. Soo-ji wonders what Ye-rim wants in exchange, but Ye-rim doesn’t want anything in return. She also tells Soo-ji that it's very unlikely that people with low ranks voted for her because it would put them in an even worse rank. At home, Soo-ji keeps thinking about what Ye-rim said and is curious about who from ranks A and B voted for her. The next day in class, Mr. Lim asks the girls to peer-review each other’s artwork and rank their friends. It turns out, the principal had told Mr. Lim to do this upon Ha-rin’s request. Do-ah then tells everyone to score their own work based on what they think they deserve. The students who are Rank D, except Ja-eun, choose a score of 35. Rank C students, except Soo-ji, pick 40, and Rank B students go for 45. Ha-rin, the top student, picks the highest score of 50. Ji-ae hesitates to go, but she knows she has to choose the lowest score. Soo-ji notices how the game has made everyone believe they shouldn't aim for a score higher than their current rank. Soo ji eventually join her peers at 40. The next morning, Soo-ji wakes up from a nightmare that she is a Rank F student again. She decides to break the system so that she can stop living in fear. In class, Soo-ji tells the girls that the vote by the app can have some errors because people in high ranks always remain in high ranks, so Soo-ji proposes they write the votes on paper and let Do-ah count them instead. Yewon, the classmate who designed the app, protests, saying the app is honest and if there were any cheating, she shouldn’t be in Rank D herself, but they still try as Soo-ji proposes. Do-ah counts the written notes, and they conclude that the app was right after all. Soo-ji apologizes to Yewon for doubting the app and leaves to submit the student work to the teacher's room. However, when Do-ah is distracted, Soo-ji replaces the stack of votes with a different one. Do-ah notices the new stack of votes but doesn’t say anything. Soo-ji uses this stack of votes and compares it with the handwriting in homework notebooks and realizes that Harin, Da-yeon, Woo-yi were the other 3 people who voted for her, besides Yerim and Ja-eun, and realizes that they are planning to play cat and mouse with her. The next day, Soo-ji works on making connections with fellow Rank C students when Woo-yi and Da-yeon bully Ji-ae, asking her to pretend to be a cat and forcing her to eat cat food. Ja-eun tries to stop Woo-yi, and she asks Ja-eun to eat the cat treats instead if she wants to protect Ji-ae. Suddenly, Ha-rin stops Woo-yi and scolds her, asking her to apologize to Ja-eun, putting up the act of a nice righteous classmate again. Soo-ji is grossed out by that and throws a pen at Ha-rin's head, then pretends it was just a mistake and apologizes to her. Woo-yi tries to hit Soo-ji for hurting Ha-rin, Ha-rin tells Woo-yi to stop, as it was an accident. Since Ha-rin is trying to act as a nice innocent person, Soo-ji leverages that to ask her to use her power as rank a student to stop the bullying toward Ji-ae and any Rank F students. But Ha-rin drops her act and says that she is just a student like them and can’t do anything else. Suddenly, the Literature teacher, Ms. Yoon Na-hee, walks into the class to give them the topic of the next exam. Ja-eun quickly hides Ji-ae, and all the students turn their heads back, acting like nothing happened. Ms. Yoon asks what's going on, but Do-ah tells her it's break time and asks her to leave the paper on the table. The teacher leaves, though she's still curious about what the students were doing. After Ms. Yoon leaves, Soo-ji gets Ji-ae's phone number. She then goes to the rooftop, and Ja-eun also follows her there. They talk and decide to work together to stop the game. That afternoon, they meet Ji-ae at the convenience store. Ji-ae cries for a while, then tells them that the class wasn’t like this at the beginning; it was Da-yeon's idea to start a game in the class. Ji-ae says the game was first meant for the class to vote for the one friend that everyone was most grateful for, and the reward was something like not having to do cleaning duty during the exam period. But over time, students began to bully those who were ranked lower than them, and violence became contagious, eventually leading them to normalize brutally bullying Rank F students. Soo-ji and Ja-eun talk about Woo-ri, the victim who was Rank F the whole Year 1 and had dropped out due to bullying. Ja-eun notices Seung-hwa and thinks she had seen him before. The next day, Soo-ji sees Do-ah in the library and thanks her for not exposing her for stealing the voting notes. She also reveals that Ja-eun told her Do-ah was the person who sent her the video of Woo-ri and Mr. Lim to her. Do-ah answers that she didn’t want Soo-ji to have to deal with the highest punishment for revealing the game to someone else and breaking the rule. Soo-ji asks Do-ah to become her ally because she notices that Do-ah actually doesn’t want Rank F people to get bullied. But Do-ah tells her that her rank and position are good now and she doesn’t want to change any of that. Before leaving, Do-ah implies that even Rank D people are difficult for Soo-ji to get as allies because they are also connected with higher-ranked people. Ha-rin, Da-yeon, and Woo-yi notice Do-ah and Soo-ji leaving the library one after the other and get suspicious of Do-ah. Meanwhile, Soo-ji, Ji-ae, and Ja-eun try to determine which Rank D student had connections with the higher-ranking students. Soo-ji realizes all the higher rank students have powerful parents that can affect the parents of lower-ranked students. That day, Ha-rin and Woo-yi attend an art galery where harin offers to buy a painting for Woo-yi. Woo-yi is excited and starts trash-talking about Do-ah, but Ha-rin harasses her and tells her to know her place. Ha-rin says that Do-ah and Da-yeon were the two people she always trust because they have known each other for years. A flashback shows Ha-rin talking about the idea of a hierarchy game in their class with Da-yeon and Do-ah during one of their family gatherings. The next day, Soo-ji, Ja-eun, and Ji-ae meet at the convenience store again. Soo-ji says they need 5 votes to be in Rank C. If the three of them vote for each other, they still need 3 more votes from Rank D students who are also looking to increase their ranks. And if there are more Rank C students than Rank D students, the pyramid will turn into a diamond, and the game will be broken. Ji-ae finds the task very difficult to achieve, but Soo-ji pulls out a folder with student information that she took photos of from the teacher's office. Soo-ji walks through the class students' profiles and shows the other two that most of the students in the class have their parents working for either Ha-rin's, Da-yeon's parents' companies, or Do-ah's dad's hospital. They then choose three students to approach. The next day, Soo-ji befriends the three targets. Ja-eun tries as well, but she is too awkward around them. Soo-ji notices Eun-jeong being especially close to Ye-rim and tries to understand the dynamics of their friendship. One day, Ms. Yoon finds Ja-eun and asks her if there has been any bullying in her class. However, Ha-rin shows up and takes Ja-eun away with the excuse of bringing her to the class before she can say anything. Soo-ji talks to Ye-won about the pyramid game app and realizes that Ye-won is insecure about being ranked D, and decides to leverage that.

Meanwhile, Ha-rin tries to threaten Ja-eun again then ja eun’s vibrate as soo ji messages her. eventually Ja-eun goes to the rooftop but doesn’t say anything about harin. Soo-ji is reading the comments from teachers about Ye-won and wonders if there is a way to hack into the students' phones to know more about them. Ja-eun thinks this is illegal, but Soo-ji thinks she should befriend Ye-won and then ask her to hack into people's phones. Soo-ji asks Ja-eun to try and talk to Ye-won. They are about to approach her then overhear Ye-rim asking Ye-won about her new Apple MacBook Pro laptop. Soo-ji checks the price of that laptop and rereads the profile of Ye-won. She doesn’t come from a wealthy background as her family owns a bakery shop, but Ye-won is described as an ambitious and opportunistic person. Soo-ji realizes that since the laptop was expensive, it was Ha-rin who purchased it for Ye-won. Soo-ji tries to call Ja-eun to stop her from following Ye-won, but she doesn’t pick up.