Yeah, editor's default encoding is UTF-8 :)
Another file encoding issue is about compiler. Erlang compiler thinks files are Latin-1 encoded (until R15, also in R16 but can be overwritten magic comments on files).

`"あ"` is three-byte in utf-8 encoded file, compiler sees it as if latin-1 and convert to three latin-1 characters. Then applies `/utf8` conversion so it results a binary of six bytes (oops).