>>5770210"Before moving to their present house, she and Koiwai used to live with his mother, and before that on an island that is, according to Yotsuba, "to the left".[12] Almost nothing is known about her biological parentage other than that she was orphaned somewhere outside Japan and then adopted by Koiwai. Hence, people often think she is a foreigner."
https://en.wikipedia.org/wiki/Yotsuba%26!#Main_charactersTo the left pretty obviously means west, it's just a matter of how far. And then there's the chance that she was born in Japan from western parents, or she's a half breed that lucked into blonde hair, or one of a dozen other reasons.
