Netflix’s hit romance K-drama, Crash Course in Romance, had fans thinking they would get a simple love story between two older characters. But the K-drama added a curveball of mystery as a series of murders occur. Fans had their speculations on who the killer in Crash Course in Romance was, and the fourteenth episode revealed the whole truth and how it is connected to Choi Chi-yeol (Jung Kyung-ho).

[WARNING: This article contains spoilers for Crash Course in Romance.]

The murders are all connected to math teacher Choi Chi-yeol in ‘Crash Course in Romance’

The K-drama tells the story of hotshot math tutor Choi Chi-yeol. Despite his fame among mothers and students, he lives in darkness. He cannot eat, sleep, and is plagued by a memory from his past. When he meets Nam Haeng-seon (Jeon Do-yeon), his life improves. Haeng-seon owns a banchan (side dish) restaurant and raises her niece Hae-yi (Roh Yoon-seo) under the pretense of being her mother.

Chi-yeol and Haeng-seon’s worlds collide as her food is the only thing he can eat. He soon learns why. She is the daughter of the woman who used to feed him out of kindness when he was a teenager. While Crash Course in Romance deals with love and the stresses of overachieving in academics, there is a murder mystery.

It all began when a high-speed metal ball destroyed Haeng-seon’s shop window while Chi-yeol was there. The mystery gets weirder when a stuck-up rich student disrupts Chi-yeol’s private tutoring class and is asked to leave. The same night, he is found dead after falling off a roof. But fans see the disguised perpetrator using a slingshot and metal ball to attack him.

The second victim is Jin I-sang (Ji Il-joo), a tutor at the academy. He used a pseudonym to expose Chi-yeol’s past on an online forum. Chi-yeol discovered the truth about what he was doing and confronted him, but fans watched the perpetrator go after I-sang and kill him as well. The killer of Crash Course in Romance was suspected to be Lee Hui-jae (Kim Tae-jung), a recluse teen, and Sun-jae’s (Lee Chae-min) brother. But there were no clear connections.

‘Crash Course in Romance’ reveals the killer is Ji Dong-hui

For some time, fans speculated Ji Dong-hui (Shin Jae-ha) is not who he appears to be. Fans feared the kind assistant to Chi-yeol could be the killer in Crash Course in Romance. When Chi-yeol refused to answer his calls, Dong-hui becomes enraged and smashed his phone. The lead detective on the case also met him and found him oddly familiar. In Crash Course in Romance Episode 12, a young man called him Jeong Seong-hyeon. He says he has lost weight but recognizes him, and Dong-hui says he is not him.

When Chi-yeol and Haeng-seong go on a boat date, Dong-hui purposely jerks the wheel and injures her. The investigation leads them to Hui-jae as the killer, but he reveals he is a witness. When the stray cat he took care of showed up injured, he began investigating. He followed the culprit and witnessed I-sang’s murder. Hui-jae told to detectives the man’s index finger was heavily calloused.

The truth about the killer is revealed in Crash Course in Romance Episode 14. While out getting trash bags, Hae-yi interrupted the killer’s attempt to kill her mother. The killer is, in fact, Dong-hui. Later in the episode, due to a fight, Chi-yeol fires him, and Dong-hui goes mad. It is revealed that Dong-hui is the younger brother of the female student from Chi-yeol’s dreams and past. His real name is Jeong Seong-hyeon.

In a flashback, Dong-hui was a chubby child fascinated with a slingshot. After hearing his mother argue with his sister, he realizes his sister jumped. Chi-yeol comforted him at the funeral, and he became obsessed. Sometime later, he was found not guilty of murdering his mother. He vowed to protect the only adult who cared for him and his sister. Years later, he bought a new identity and got a job at the tutoring school.

Hae-yi is the only one who can identify the killer in the K-drama

Dong-hui has been killing people who pose a threat to Chi-yeol. He wants to kill Haeng-seo because she is distracting Chi-yeol and making him forget about his sister. After Hae-yi interrupted Dong-hui, he catches her and kidnaps her. Using his pen, she broke free from the tape and escapes again. But she is struck by a car, and Dong-hui fakes a suicide note to cover his tracks. In the hospital, she is in a coma. After the police question Chi-yeol, learns about the callous, and hears the name Jeong Su-hyeon, he realizes something.

Haeng-seon found reddish-orange ink on Hae-yi’s hand. Chi-yeol is also perplexed until he is in his office and reviews notes written by Dong-hui. The ink is the same color. In a flashback, Don-hui gave Chi-yeol his pen to borrow, which he says was his sister’s. The pen is the same one Chi-yeol gave Su-hyeon before her death. He realizes the truth about Dong-hui.

Later, he invited him to his home under the ruse of patching up their relationship and rehiring him. He used it as an excuse to hold his hand and feel Dong-hui’s calloused finger. Chi-yeol now fears Dong-hui is the killer and will hurt his newfound family. Crash Course in Romance K-drama has perplex murder mystery.

Crash Course in Romance is available on Netflix.