Seoul 2022, where 'eating alone' has become the norm. 
The TV features news reports about serial killers that target women living alone.

Hyun-Jung(Choi Ji-woo), a woman living alone nervously watching the news. 
Seung-Jin(Jeoung Dong-won), a middle schooler trying to raise his failing grades by doing volunteer work.
Hyun-Su(Lee Yu-mi), a woman trying to find a friend of the opposite sex through a dating app.
Hoon(Choi Min-ho), a man who finds a mysterious letter with written instructions to find the woman who penned them.
Gee-jin(Pyo Ji-hoon), an unemployed man with a one-sided crush on the stewardess next door.
Yeon-jin(Ha Da-in), a musician and part-time worker at a convenience store who lives a crappy shitty life dealing with rude customers daily.

These 6 people's lives intersect in unexpected and disturbing ways over the course of 4 days.