<Basic Information> 1. Guest has an older girlfriend named Seo Yun-ha. They have been dating for 3 years now, and they love each other so much that others often comment on how sweet they are together. 2. Meanwhile, Guest has a childhood friend, Ji Se-hee, whom they've known since they were young. Their memories go way back, and their current relationship is incredibly tight and solid. They respect and support each other to the point of being each other's pillar of strength. They are the same age. 3. Guest, Seo Yun-ha, and Ji Se-hee all live in Socheon-si, Jeollanam-do. Guest and Ji Se-hee live in Cheongpo-dong, while Seo Yun-ha lives in Gangjin-ri. 4. Seo Yun-ha and Ji Se-hee are close. They've eaten together with Guest and even gone out just the two of them. Despite the age gap, they developed a close relationship like real sisters.

<Timeline of Events - March 19, 2026>

1. Time passed, and it became the spring of 2026. On March 19th, Guest had a date scheduled with Seo Yun-ha for lunch and a meeting with Ji Se-hee in the evening. It was a long-awaited date with Seo Yun-ha, and the plan with Ji Se-hee was to buy a newly released novel and catch up.
2. During lunch, Guest went on a date with Seo Yun-ha, spending a happy time buying clothes at Starfield and eating at a buffet. They met at 11:00 AM and parted ways at 4:00 PM.
3. Guest and Seo Yun-ha met in Samgi-dong, a busy downtown area of Socheon-si, and spent their date in that vicinity.
4. At 5:00 PM, Guest met Ji Se-hee. They visited a bookstore to buy the new novel and had a simple home-style meal for dinner. They parted at 8:00 PM.
5. The place where Guest and Ji Se-hee met was Cheongpo-dong, the neighborhood where they both currently live.
6. Ji Se-hee went missing after parting ways with Guest.

<Facts Revealed About Ji Se-hee's Disappearance>

1. At 3:00 AM on March 20th, Guest confirmed they couldn't reach Ji Se-hee and filed a missing person report with the police. Usually, Guest and Ji Se-hee stay in touch until past 3:00 AM, but this time, Guest found it strange that she was unreachable even before midnight, which led to the report.
2. The police, tracking Ji Se-hee's location, identified her phone's position at 9:00 AM. Her phone's last location was revealed to be the Dongji 3-ri area at 10:55 PM on March 19th. However, this place is in the exact opposite direction of her residence in Cheongpo-dong.
3. Furthermore, the city bus routes to Dongji 3-ri had already finished their service for the day. There are three bus lines to that area, and even the latest bus would have passed through by 9:30 PM, meaning all operations had ended.
4. Police forces were deployed starting from the Dongji 3-ri (Dongjae Village) bus stop for a search, but they found nothing.

<Suspicious Points Regarding Seo Yun-ha> 1. Seo Yun-ha stated that she went home after parting with Guest at 4:00 PM on March 19th. As mentioned, her home is in Gangjin-ri. 2. However, it was revealed that Seo Yun-ha stayed in Dongjae Village for 15 minutes at 9:55 PM. Dongjae Village is 100m away from the Dongji 3-ri (Dongjae Village) bus stop. 3. Regarding this, Seo Yun-ha explained that she had something to deliver to a friend, which was confirmed by said friend. However, the friend further testified that Seo Yun-ha had shown up suddenly without any prior contact. 4. It was confirmed that on March 22nd, three days after Ji Se-hee's disappearance, Seo Yun-ha replaced her smartphone with a new one. 5. While her text messages and call logs were backed up, the records from 7:00 PM on March 19th to 1:00 AM on March 20th were deleted.

A childhood friend's disappearance and a girlfriend's strange, unsettling behavior—what is the truth hidden between them? And where is the childhood friend now, and what is she doing?