Guest and Seo Hyebin first met in high school. At first, they were awkward and couldn't speak to each other, but they gradually got to know one another and spent more time together. Eventually, they became attracted to each other and started dating.

Their relationship continued through university. Hyebin not only waited for Guest while he was in the military but also threw a small celebration for him when he was discharged. Guest also gave Hyebin bouquets and letters to thank her for waiting, and their bond grew even stronger. After graduating from university, they continued dating and finally married at the age of 28.

It was a very sweet married life. They smiled at each other over breakfast every morning, hugged tightly when they returned from work, and talked about their day. It was a marriage that provided small but certain happiness. As those days continued, it felt like their happiness and love would last forever.

However, this was shattered in the year they turned 30.

Friday, April 3rd, when the cherry blossoms were starting to bloom. This was the day Guest and Hyebin promised to go on a date in the park after work. Both Hyebin and Guest had been looking forward to this day. They still felt the same emotions they had when they first started dating, and they felt like they were returning to the days of their fresh first love. Because of this, they promised to meet for their date immediately after work.

That day, Guest finished work as usual, but Hyebin did not return even after 10 PM, and there was no contact. It was strange. She usually finished work at 6 PM and was home by 8 PM at the latest. Hyebin was the type to always send a message with an emoticon if she was going to be late, but there was nothing today. Sensing a bad omen, Guest filed a missing person report.

1. Last Sighting Before Seo Hyebin's Disappearance

Upon investigating Seo Hyebin's last movements, she was last seen walking with a smile at a bus stop three blocks away from the apartment where she and Guest lived. She was spotted walking with a bright expression. Perhaps that smile was out of excitement for her date with Guest.

2. Seo Hyebin's Mysterious Phone Calls

On the morning of April 5th, Guest received a call from an unknown number. That call was made by the missing Seo Hyebin. However, instead of Hyebin's usual cute voice, a low and cracked tone was heard, giving Guest a sense of unease.

Seo Hyebin said only one thing: "Guest, I'm doing well right now. Everything is fine, right?"

It was impossible to tell where she was "well." It made no sense for a missing person to call from an unknown number. Furthermore, if she was able to make a call while missing, it seemed she should be able to return home. However, she simply made the call, said that one sentence, and hung up.

On April 7th, she called a friend. But all Hyebin said was to ask them to take good care of Guest. Then, on the afternoon of April 13th, she called Guest one last time, remained silent for 10 seconds, and then the call ended. After this, all contact with Seo Hyebin was lost. Tracking the calls revealed the following facts:

Seo Hyebin's location was identified as Nakcheon-si, Gyeongsangnam-do on April 5th; Dongchung-gun, Gyeongsangnam-do on April 7th; and Gamgye-gun, Gyeongsangnam-do on April 13th. These three locations are southeast of Guest's home in Incheon and correspond to a route moving from west to east along Highway 11. Why did she make calls along this route? Is it possible the person who called wasn't actually Seo Hyebin?

3. Seo Hyebin's Phone Powered On

There was another incomprehensible occurrence. At 1 AM on April 14th, Seo Hyebin's phone was turned on.

However, from the day of her disappearance on April 3rd until the 13th, it had definitely been off, and calling it only resulted in the automated message "The power is turned off..." Someone had turned the power on. It could have been Seo Hyebin, or it could have been someone else.

Seo Hyebin's phone location was traced to the vicinity of Neungtong-gol. This was a remote area 71km away from Gamgye-gun, Gyeongsangnam-do, where the previous day's call was made. Neungtong-gol is a mountain village located north of Gyeonggang-si, Gyeongsangbuk-do, and the specific signal was picked up in a particularly secluded part of that village. A call was placed, but it was disconnected after the sixth ring. Who exactly turned on Seo Hyebin's phone?

Seo Hyebin's disappearance. Due to these mysterious points, the case began to sink deeper into a labyrinth.