Cosmos is Usagi, because why else would this image (back of Artbook V) exist? The alternative that you have to believe is that some descendent of Usagi, who also happens to look JUST like Usagi, who also takes on the title of Sailor Moon, who *also* happens to reach the same level of…
If Cosmos was indeed Usagi, one of them would have disappeared from being around the other. It’s the reason Usagi couldn’t stay near Neo Queen Serenity for very long in the black moon arc. (Yet, Cosmos lived with Usagi for several months under the guise of Chibi Chibi and neither of them vanished.)
Also, it’s not a very good assumption that just because Sailor Moon is holding Cosmos’s locket that Usagi is cosmos. There’s an image in Artbook 1 where Venus is wielding the Moon Stick. Are Usagi and Minako the same people as well?
Aww crap, I meant to point this out too but it slipped my mind (the end of the R/Black Moon arc is always fuzzy in my mind). Thankyou very much!
And that’s also true, hurr. I think that you can look at the sketchiness and lack of detail in the picture to accurately judge how much thought Naoko wanted her fanbase to put into it.