Locked Guest Room

In the twelfth lunar month of winter, a bizarre murder occurred in the hot spring hotel "Tinglanju" at the foot of Qingfeng Mountain. Guest Wei Mingyuan was found dead in Room 206. The doors and windows were all locked from the inside, and the door chains were intact, forming a seemingly impossible secret room. After the police intervened in the investigation, as the suspects emerged one by one - the debtor contractor, the mysterious lover, the overly calm wife, the suspicious manager - the truth pointed to the most inconspicuous person. The secret room techniques were cracked one by one, and hidden behind the cases was a past three years of blood-for-blood feud between the father and his father. Core puzzle: How to create a secret room? Who is the murderer? What's the motivation?