My Perfect Stranger

Curiosity leads Hae Jun to discover a time machine. He learns to operate it with ease and begins his adventures across time. Yoon Young works as an editor for a famous writer and neglects her mother. But then she gets a shocking phone call that her mother is dead.

Despite her confusion about the current situation, Yoon Young recognizes a small possibility of altering the future after a chance encounter with 19-year-old Soon Ae, prompting her to follow her closely. Soon afterward, Yoon Young learns about the mistreatment that Soon Ae is facing from the other kids and also notices that some of the children resemble those she knew from the future.

Yoon Young was able to enter school thanks to Hae Jun's help. As soon as she began her classes, she realized that one of her classmates was the future Ko Mi Sook. However, she was unaware of the danger that Ko Mi Sook posed, as she was extremely clever. Hae Jun ensured that Yoon Young remained at school until he could pick her up, but when he returned, Yoon Young was nowhere to be found.

With the day drawing closer, Hae Jun experiences mounting anxiety over the possibility of failing to prevent the murder, given his limited information and unexpected developments. While the school is on a field trip, a new student teacher is introduced, whom Yoon Young finds strangely familiar. Later that night, while alone at home, Yoon Young recalls the true identity of the student teacher.

Now that Yoon Young has developed trust in Hae Jun, she believes it's crucial to disclose her relationship with Soon Ae and Hee Sub to him. With the missing pieces of the puzzle given to him, Hae Jun finally comprehends the reasons behind Yoon Young's fixation on Soon Ae. More importantly, Hae Jun proposes an alternative perspective on what could have occurred to Yoon Young's mother, leaving Yoon Young stunned at her own foolishness for losing hope.

Hae Jun feels it's unnecessary to share what he saw with Yoon Young, complicating the situation. He grows agitated as events deviate from his expectations. Meanwhile, Yoon Young is surprised by Soon Ae falling for Hee Sub despite her attempts to break them apart. Later, Yoon Young understands why Hae Jun hid things from her, and as she talks, something clicks in Hae Jun's mind.