Episode 4 recap: Shan Yu persistently asks Min Ying for the reason behind their breakup.
Zheng Zhe's meeting with Shan Yu reminds him of a day ten years ago when Shan Yu and Min Ying started dating. Shan Yu had accompanied Min Ying home, and the sweet scene between them stirred jealousy in Zheng Zhe's heart. Now that both Shan Yu and Zheng Zhe are in the same laboratory, Shan Yu asks Zheng Zhe when he started dating Min Ying. Instead of giving a direct answer, Zheng Zhe hopes that Shan Yu will give up on Min Ying since they are already together.
After Shan Yu returns home, holding a candle, he desires to go back ten years and change the present situation. At this moment, Yin Xun, who is crying, approaches him. Yin Xun is aware that Shan Yu has cancer and has even arranged an appointment with a specialist, hoping that he will seek medical treatment and undergo surgery. Shan Yu superficially agrees but locks himself in his room, leaving a letter behind. Through the closed door, he asks Yin Xun if she believes in time travel. Yin Xun pretends to believe but, upon realizing the absence of any sound in the room, rushes in and discovers that Shan Yu is nowhere to be found.
Shan Yu returns to his class ten years ago and sees Yin Xun, who is sleeping with his head on the desk. He leaves a note specifically for Yin Xun, and suddenly, this fragment of the note appears in Yin Xun's memories ten years later. He hurriedly searches for it and finds that the back of the note states that on this day in 2018, Yin Xun will receive this note and understand its meaning.
Shan Yu also visits the professor and inquires about Min Ying's plan to go abroad. From the professor, he learns that Min Ying has given up on going abroad and has said that as long as Shan Yu doesn't leave, she won't leave either. In an instant, Shan Yu returns to the present and sees from his social media feed that Min Ying is going to take wedding photos today. He immediately goes to find her. Shan Yu relentlessly questions Min Ying about why they broke up and why she chose to marry Zheng Zhe. Min Ying becomes anxious and wants to leave. Suddenly, Shan Yu experiences a severe headache and a nosebleed. Frantically, Min Ying empties her bag to find tissues to wipe Shan Yu's blood. As Shan Yu holds Min Ying's hand, he continues to ask for the reason behind their breakup, and unfortunately, this scene is witnessed by Zheng Zhe.
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