I investigated this subject back when the name "Wada Shinichi" came up but I found very little sources regarding the changes done in the first Japanese editions of "Study in Scarlet".
One source is this tweet with a compilation of names used in those editions:https://twitter.com/221bjxxxsxxxx/statu ... 5459250176
Mind that these name changes are only for "Study in Scarlet" and a Japanese name for Moriarty doesn't exist because he wasn't introduced until much later when the "Japanized" names were discarded in favor of the original, English naming.
Translation of the tweet (list of Japanese Holmes character names)
Author is the author of the translation and the names used in each
(Author): Nanyo Mizuta (Names used): "Great Detective", "Medical Student"
(Author): Kyushiro Honma (Names used): "Horimi", "Wada"
(Author): Yakoro (Names used): "Holmes", "Watson"
(Author): Anonymous (Names used): "Honda", "Wada"
(Author): Anonymous (Names used): "Tairoku Komuro", "Wada Shinichi", "Sekido Reiko", "Tsutomu"
(Author): Sanjin Kazaha (Names used): "Horimi Inokichi", "Wada Shinichi"
It's unknown who "Sekido Reiko" and "Tsutomu" are supposed to be unless they are Gregson and Lestrade, the two police detectives working on the case.