On File 599 of Detective Conan, Eisuke has let out a name that appears to be the real name of his Sister. That name is Hidemi-neesan. The interesting thing is that the first character in this name is exactly the same as the first Character in Eisuke. When I looked up this character (瑛) in the dictionary, I found out that it means (sparkle of jewelry, crystal). Also I found that it does not have the reading "HI DE", so it's possible that Aoyama Gosho has forced this reading to this Kanji, because it's similar to (英).