Sora is the twin sister of Yamato Tokio and was just called "Sora" when introduced in the Bros. Comics.
The wikia has the following pages on her;
Her family name of "Yamato" is a name of a province that exists in Japan, it is also one of many names used to refer to Japan itself.
Her name of "Sora" can be translated to mean "sky". also its worth noting that names ending in "ra" also indicate a "daughter", which is also the same reason for Putera's name ending in "ra". This is in contrast to "ro" indicating a "son" (see Narugami Kyoichiro as an example).
Several characters within the show use "san" to address Sarah in the Japanese show, calling her "Sora-san"(大和ソラさん). "San" indicates a level of respects between individuals. Her us of "Narugami" in the Japanese dub for Merlock (calling him by his family name instead of given name) indicates they are not close friends, though his use of "Sora" instead of her family name of "Yamato" would suggest they are. Though it also could be done to avoid confusion between her and Tony when addressing either of them.
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|Antagonists||Petra Fina Dagmar | Dino | Mite | Dark Lord|
|Other||Dr. Bernard Goodman | Jillian Grey | Merlock Holmes | Old Timer | Z•Z|
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|Other||King Arthur | Marie | Lee | Unnamed Historic Figures|