First go to the original journal web page for the paper in question. That might have more information. It may have their full names, links to other papers by them, and will almost always have their affiliation at the time of submission of the paper.
You can also search the usual literature databases for other papers in the same field by the same author: other journals may have the author' full names; furthermore, more recent papers will have their most recent affiliation.
Once you've got their most recent affiliation, you can then search that institution's website for the authors' home pages.
In this particular case, the paper is listed here. By clicking on the author names, I find that Hama Masaki is one of the names you are after: by using the distinctive "Pisot" from the paper title, I can narrow down to an individual. A bit of searching for the full name and Pisot gets me what I think is a different form of the same name: 浜, 正樹 ; searching for that with Pisot gets me what looks like the author's home page. This should be enough to enable you to contact that author.
And for goodness sake, don't go directly citing a paper that you haven't read. I'm grateful to Peteris for the comment on the original question that deserves higher profile than a comment: indirect citations are one of the ways in which myths are born and are spread: see this excellent read on "Academic urban legends" from Ole Bjørn Rekdal. (full text here)