While Jeon Do-yeon and Jung Kyung-ho made their first bed, Shin Jae-ha turned out to be the killer of the iron beads Murder case. In the twelfth episode of tvN's Saturday-Sunday drama ⁇ Crash Course in Romance ⁇ , which aired on the 19th, Nam Haeng-sun (Jeon Do-yeon) and Choi Hwang Chi-yeul (Jung Kyung-ho) reconciled after their first fight and spent the night together. On this day, Lee Hee-jae (Kim Tae-jung) was urgently arrested as a suspect in the Murder case, and Jang Seo-jin (Jang Young-nam) headed to the police station after hearing the news. Jang Seo-jin asked the police whether he had a warrant or not, and he took out Lee Hee-jae's psychiatric certificate from his bag and explained that he was unstable and that the reason he received a US visa was to find a cure. Choi Hwang Chi-yeul (Jung Kyung-ho) and Jeon Do-yeon (Jeon Do-yeon) were fighting again due to Shin Jae-ha while returning home. The South Korean ship broke the silence, saying, "I was excited about Ji-chan's story," but Choi Hwang Chi-yeul said, "Stop talking about it. The next day, Choi Hwang Chi-yeul couldn't contact Nam Haeng-seon due to his busy schedule. However, Ji Dong-hee deleted the SMS of the south line in secret, Choi Hwang Chi-yeul in the meeting, and because of this, Misunderstood that Choi Hwang Chi-yeul ignored his SMS. After the schedule was over, Choi Hwang Chi-yeul tried to take Ji Dong-hee, but he could not do it because of Ji Dong-hee's extreme rejection. Instead, Ji Dong-hee sat at the steering wheel saying that he would take Choi Hwang Chi-yeul home. Choi Hwang Chi-yeul asked Ji Dong-hee, "Do you have any inconvenience with Nam Haeng-sun?" He said, "I want you to get along well. If you do not laugh, there is a cold place. I advised him to smile a lot because he could do Misunderstood. In particular, Ji Dong-hee said, "I do not think she dreams of a girl these days." Choi Hwang Chi-yeul's answer, "Yes." Ji Dong-hee denied that he was a classmate who called himself Jung Sung-hyun. Jung Sung-hyun is a student of Choi Hwang Chi-yeul and a younger brother of Claudia Kim who has taken her own life. Choi Hwang Chi-yeul arrived at the front of the house in time for the dawn chapter to relieve the anger of the south line. The two reconciled at the dawn chapter and solved Misunderstood that they ignored the contact. Since then, Choi Hwang Chi-yeul has taken the southbound line to his yacht off the coast of Incheon, and Choi Hwang Chi-yeul and Ji Dong-hee, who had to digest the next schedule, also drove the yacht. However, Ji Dong-hee deliberately broke the steering wheel while Choi Hwang Chi-yeul was away for a while, hurting the south line. With this incident, the South Line began to doubt Ji Dong-hee again. Choi Hwang Chi-yeul took him to his house again because he was worried about the South Line. When he finished hand disinfection, he grabbed the South Line and said, "Can not you sleep today?" The next morning, Nam Haeng-sun woke up in Choi Hwang Chi-yeul's bed, and Nam Haeng-sun was caught out of bed facing Nam Hae-yi (played by Noh Yoon-seo) in front of her house, and Nam Hae-yi went to school, saying, "Change your clothes and go out, or Auntie will make a lot of fun of you." Lee Hee-jae denied the charges, saying, "I didn't kill him. I saw him. I'm a witness."