Gekka is too likely to be a name at some point (There's one in Kyouran Kazoku Nikki already, albeit with a full name) so I'd rather just change the four tags.
The circle/site seems to be called Takemi Kazuki, and it lists the "participants" as jungetsu_hoko and ppr, although ppr has both a separate homepage and separate pixiv page. I've populated jungetsu_hoko's artist page, so that anyone doing find artist will get the right one.
I think this one is done now.