Episode 16 of "Friendly Rivalry" kicks off with Seul-gi dashing towards the swimming pool, the scene of a prior dramatic encounter where she had leaped into the depths, only to be rescued by Je-yi. During that fateful moment, Seul-gi cunningly persuaded Je-yi to ensnare Tae-jun by using her as bait, aiming to expose his repetition of a past crime – the murder of her father.
Je-yi initially intended to mirror Tae-jun's previous modus operandi by introducing Seul-gi to a member of the exam committee, much like he had done with Je-na. However, her suspicions were aroused when she noticed a hospital employee among the committee members. It transpired that Je-yi had duped Seul-gi by giving her vitamins instead of drugs and had surreptitiously submitted an application on her behalf.
Later, Seul-gi crosses paths with Byeong-jin, who reveals himself as the mastermind behind the punctured car – an act orchestrated as part of a deal with Tae-jun. Seul-gi proposes an audacious business venture: selling leaked final exam questions to affluent families. They embark on amassing funds from eager clients and devise a scheme to obtain the stolen exam papers.
Meanwhile, the math teacher surreptitiously hands over the exam papers to the hospital employee stationed at the committee facility. The employee stages an urgent request for a blood delivery from Tae-jun's clinic, luring him to the scene. She then cunningly conceals the exam paper inside a pill and passes it to Tae-jun. However, Seul-gi and Byeong-jin intercept Tae-jun's ambulance, threatening him to surrender the pills. Just as the tension peaks, Je-yi arrives, feigning intervention, which forces Seul-gi to ingest the pill. Unbeknownst to Seul-gi, Je-yi secretly drugs her.
Seul-gi is whisked away to the operating room, while Byeong-jin grapples with the wrath of his impatient clients. Tae-jun refuses to operate on Seul-gi, prompting Je-yi to step in. The pill is successfully extracted from Seul-gi's system, and Byeong-jin proudly presents it to the eager clients, including Choi Gyeong and A-ra.
Their elaborate scheme crumbles when Tae-jun gives Je-yi the genuine exam questions, rendering their stolen version obsolete. To add insult to injury, the questions contained in Byeong-jin's pill prove to be vastly different from the actual exam. Seul-gi, who misses her exam due to the surgery, is left heartbroken and defeated.
After the exam, Choi Gyeong employs her legal expertise to liberate Ye-ri from the clutches of a hostess bar owner who had been coercing her into returning. Meanwhile, Byeong-jin finds himself in deep trouble with his disgruntled clients.
Seul-gi ultimately decides to withdraw from school, her journey diverging sharply from that of her sister Je-yi, who triumphantly tops her exams with an impeccable score. Tae-jun, celebrating Je-yi's outstanding achievement, steps into the limelight for an interview, only for the broadcast to be abruptly halted by a harrowing live feed: Je-yi and her sibling Je-na, in a harrowing leap, plunge from a building window into a river below. The following morning, Je-na is miraculously discovered, yet Je-yi remains elusive, her absence leaving Seul-gi's heart shattered into pieces.
It gradually comes to light that Je-yi had secretly recorded Seul-gi's surgery, unwittingly exposing Tae-jun's deep-rooted corruption. Scandalous headlines erupt, revealing Tae-jun's desperate attempt to illegally obtain the challenging college entrance exam questions for his own offspring, ultimately leading to his swift arrest.
Days turn into months, and Je-yi's body remains unrecovered, her absence a lingering pain. Tae-jun serves his time behind bars before eventually regaining his freedom. Meanwhile, Ye-na, after taking a humble job at a restaurant, catches a break and is offered a promising new opportunity. Deeply inspired by the harrowing ordeal of Ye-ri, Choi Gyeong makes a resolute decision to embark on a legal career. Seul-gi, on the other hand, continues to reside with her stepmother, diligently preparing for her college entrance exams, her academic performance flourishing as she steers clear of drugs.
One serene day, a mysterious package arrives at Seul-gi's doorstep, revealing a captivating photograph of a serene seaside locale. In the poignant closing scene, a figure—undeniably Seul-gi—rides a skateboard towards the horizon, towards a place where Je-yi might still be, the episode drawing to a bittersweet close amidst a tantalizing hint of hope.
