No one had expected to suddenly hear something like that, and they all froze.
A moment later, the waitress was the first to recover. Delighted, she said, "I knew it! There's no way Mr. Jiang Xia could be the murderer!"
"Wait, wait." Inspector Yokomizo hurriedly pulled a notebook from his pocket and fumbled it open. "Why do you think he's the murderer?"
Jiang Xia kept walking, leading the group into a stairwell that could not be seen from the lawyer's position before finally stopping.
Then he pressed the elevator button and continued unhurriedly, "When I left the room just now, I saw a short piece of thin thread on the floor, around three or four centimeters long. There was a knot in the middle, and both ends looked like they had snapped. Also, there was a broken section of chain behind the door."
"..." Inspector Yokomizo had not noticed any of those details at all, so he discreetly looked toward his subordinate.
The subordinate who had glanced around the room earlier nodded. "Those things were there."
Jiang Xia said, "With the right tools, it is easy to create a 'locked room' even after leaving the room.
"After killing Ms. Usui, the murderer cut through one of the iron rings on the Door Chain. He placed the broken iron ring on the floor behind the door, then inserted the broken bolt into its groove. After leaving the room, he turned back and pulled the door shut until only a narrow crack remained.
"Then, through the door crack, he only needed to use a piece of thin thread to tie the broken Door Chain back together, creating the illusion that this was a locked room with the Door Chain in place.
"The murderer probably cut the second Iron Ring from the end