Siheyuan: Decrypting Privacy, Starting with a Chicken

At the gate of the courtyard, Banggan picked up a letter with no addressee. The content inside was simple and clear, "chicken = disaster" Who wrote the letter? Who is the recipient? Anyone who sees the letter, this letter is related to everyone who receives the letter. Is it premeditated or a coincidence? Everyone in the courtyard has their own thoughts. Coincidentally, everyone who receives the letter has done what is written in the letter. Who wrote the letter to whom? Those who read the letter had trouble sleeping and eating! This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.