Goodreads Librarians Group discussion

I don’t quite dare to rename the profile without a discussion, but i can’t find the name of Ema Toyama spelled with a ō on any book cover. It is Ema Toyama most of the time, sometimes Ema Tohyama, but not really Ema Tōyama. (I can't find here at the Library of Congress, only in the Deutsche Nationalbibliothek.)

And yes, the o is pronounced as a long ō/oo/oh, and yes, the Wikipedia page is at Ema Tōyama, but that is not how the name appears on book covers.

eta:
E.g. here you can zoom into an original Japanese cover, and no macron on the o in sight.

OK, now i am confused.
Library of Congress has both variants, with their author profile (so to say) using Tōyama, and the author of the individual works as Toyama. Huh?