In the ninth episode of Absolute Value of Romance, Eui-ju sits beside Woo-su on the bus heading home, her thoughts swirling around his last comment about wanting to understand her better. Eui-ju lies to Woo-su about contemplating the relationship between Pythagoras and Hippasus, and he proceeds to give her a detailed explanation, making Eui-ju realize just how deeply obsessed Woo-su is with mathematics.
On the way home, Eui-ju starts to think about her feelings for Woo-su. Back at home, Eui-ju's mother asks to meet Woo-su to thank him for taking her to the hospital. Although she speaks negatively about him, Eui-ju unexpectedly finds herself defending Woo-su. Confused by the sudden change in her feelings, Eui-ju decides to avoid him.
The next morning, Da-ju talks to Woo-su over breakfast about his Olympiad peer, who was recently announced as the winner of a Fields Medal. He complains to the other teachers about Woo-su not living up to his potential as a mathematician. Gi-jeon argues with Da-ju while Dong-ju and Woo-su continue eating breakfast in silence.
At the same time, Eui-ju waits outside the teachers' house, hoping for Woo-su to show up. She is disappointed to learn that he has already left for school. Later in class, Eui-ju starts looking at Woo-su romantically and quietly takes note of his behavior without realizing it herself.
Elsewhere, Eui-ju talks to Go-ya about her newfound feelings. Assuming that she is talking about Gi-jeon, Go-ya tells her friend that she is falling in love. She encourages Eui-ju to embrace her feelings and pursue him. Around the same time, Eui-ju and Go-ya learn that Jennie plans to go on a long field trip as part of a report-writing project for extra credit.
Later, Eui-ju finds Go-ya reading Dong-ju's story and encourages her to speak to the Korean Literature professor. However, Go-ya becomes jealous after noticing how easily Eui-ju talks to Dong-ju. She blames Eui-ju for not inviting her into the conversation and wrongly assumes that Eui-ju has feelings for him.
That night, Eui-ju begins writing a new chapter of her BL story. Without realizing it, she starts writing Woo-su's character as the main lead. She also introduces Da-ju's character as another love interest for Dong-ju's character. Eui-ju is shocked by the sudden shift in the story and by the fact that Woo-su's character has now become the male lead.
As she delves deeper into her writing, Eui-ju envisions herself as Woo-su's love interest, and suddenly feels a wave of panic wash over her. Without hesitation, she sends the draft chapter to Woo-su, who is just as surprised by the sudden shift in his character's role in the story.
The next day, Go-ya notices Eui-ju speaking in hushed tones with Dong-ju and feels an even greater sense of jealousy. She confronts Eui-ju about approaching the teacher and scolds her for it. Go-ya presses Eui-ju to finally reveal the truth about her crush. Although Eui-ju asks her to trust her, Go-ya remains upset, causing tension to seep into their once-close-knit group of friends.
That night, Eui-ju lies in bed, reflecting on Go-ya's reaction and wondering if she can mend their friendship. The following day, she heads to a cafe to study but suddenly realizes her true feelings for Woo-su. While there, Eui-ju spots Woo-su at the cafe and starts to indulge in fantasies about him. However, she sees Woo-su talking to another woman and immediately feels a pang of jealousy as the episode ends.
In this tale of friendship and unrequited love, Eui-ju's emotions are put to the test as she navigates the complexities of her feelings and the dynamics of her friendships.
