Masaya Miyashita is the real name of the artist using the pseudonym "SHIYAMI" or "Yasamata Shiyami" in the database. A number of years ago, this artist had been arrested for publishing doujinshi. I don't know if the regulatory troubles had resulted in the artist using multiple pseudonyms or different ones since 2008 (how annoying!). An overview of what happened is at: http://zerohiei-rgg.livejournal.com/3581.html
The circle "S-Plus" is the most stable reference for this artist. There is also the circle "S-Plus!" in the database that needs to be deleted. I uploaded the credits page to the one doujin entry that used that "S-Plus!" circle name. The artist used various names such as "SHIYAMI" or "Yasamata Shiyami" for doujin and PC HCG works while maintaining his professional artist name as Masaya Miyashita.
See the artist's archived homepages for proof of the various names he used: http://web.archive.org/web/20041208143601/http://home.e-catv.ne.jp/shiyami/index.html http://web.archive.org/web/20041209095954/http://home.e-catv.ne.jp/shiyami/dozin.htm
So, do all the different works by the artist as "shiyami" and "yasamata shiyami" get aggregated under the artist's real name of "Masaya Miyashita"? It would be quite a change for a bunch of entries.