Though the three new characters had the last suspicion, I would not assert that Bourbon must be among them. It was clear when passing through an overpass and RX-7 and approached, Ai felt something unusual. Since Vermouth stood a little far on the overpass, I exclude her and get 4 suspects, namely Amuro, Kogorou and Ran in the car, and Sera.
In this series, Ran had some strange behaviours.
1. At the beginning, she didn't wear a star pedant. Changes of accessories may be clues that the person has been switched, for example, fake Araide and the real one had different styles of eyeglasses.
2. Ran didn't recognize sera's phone number. As far as I can remember, her phone could show caller IDs.
3. Ran mentioned the tracing glasses and asked Ai to come( She couldn't forsaw Okiya would take a part).
4. Ran knew Sera would come but didn't wait for her.
When RX-7 passed, Okiya seemed to notice sth. Probably, it was Amuro, but Ran, seated next to him also appeared in the pic and cold sweat started out on her face. I think it is a passable explanation that Okiya figured out Fake Ran and Amuro smelt out she was a little strange. Then he huged her to set a bug or make sure she was not Ran(If Bourbon was an adult male, his weight must be much different from a girl's.)
Okiya wore his bluetooth headset after Conan was safe and I didn't see his phone ring. So if he was not monitoring someone, I assume he made a call, likely to Amuro or Sera, to warn of Fake Ran. Vermouth was talking with Fake Ran.
But there are some holes. I wonder if Conan and Kogorou can't tell a fake Ran.
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