In Monogatari Second Season Episode 24 at 08:35, Kaiki referred to a person as a Cat's Eye. I found a movie, a road marking, and a jewel. Whatever he is referring to, I don't think it exists in western culture. Does anyone know what Kaiki meant when he referred to the person as a Cat's Eye?
As for what the person did in order to be referred to as a Cat's Eye:
The person was able to slip an envelope into Kaiki's hotel room. Kaiki says that it shouldn't be possible since 1. they shouldn't know where Kaiki is currently staying, and 2. the hotel room is locked.