Sera knew Conan and Ran's identities before they introduced themselves. Although she claimed to know Ran from Karate tournaments, she recognized Conan as a detective and anticipated his skill. Sera admits that she has met Conan before, but she can´t tell him until "the time" comes.[24] Since Conan didn't exist until Shinichi shrunk, Sera must have met Shinichi some time in the past, and she recognizes him as Conan. The meeting was probably a significant time ago because Sera, while blushing, asks Conan if he once met a girl "a long time ago and could never forget [her]"[25] and gets annoyed when he says he can't recall someone like that. Conan realizes he met Sera before because he finds her snaggletoothed smile familiar,[26] but she refuses to tell him where they met prior.[24] Ran appears to have met Sera as well because Sera's figure as she runs away reminds her of "sounds of rippling waves, as if some sort of magic were at work."[27]
In Chapter 771, it is revealed that she also knows Professor Agasa, although she calls him "Professor what's his name".