Envelope Mystery

In the story, the protagonist is a young man who lives alone and lives a lonely life at home every day. One day, he received a mysterious envelope telling him that someone was going to kill him. In the following days, the protagonist fell into a series of panic and doubts. He didn't know whether the news was true or false, and he didn't know how to deal with it. Ultimately, he decides to face his fate alone, uncovering a shocking truth.