It appears that toranoana is currently being used for both the artist circle, as stated in the wiki article, and also for artbooks published by this company: http://en.wikipedia.org/wiki/Comic_Toranoana
Unless I'm missing something, they do not appear to be the same. The wiki article doesn't list ishikei or tomose shunsaku as artists in the circle, and it's newer than some of the posts by both of them which have been tagged with it since their upload.
What do we want to do here? If they really are different, they obviously shouldn't use the same tag.
Updated by Daijin