Nope, Kiyohiko Azuma didn't draw that. I just googled it and it was drawn by the author of Pretty Neighbor, and also this doujin about Osaka. This dude really can draw with a style similar to Azuma's.
In fact, that page you posted comes from Pretty Neighbor number 7, even though it's not porn.
I don't know if the translation is real, but may be since a lot of people seem to want to know where Yotsuba came from in the canon of the manga, which is a question I don't think will ever be answered. In fact, I don't think we need it answered, and Azuma himself may not know.
I found a theory on Tumblr:> There's theories that she's from North Korea because she's afraid of targets and whenever she hears something loud she goes "we're under attack"
I think that makes sense, but also I think coming up with theories is missing the point. Yotsuba is a story about very simple things, and introducing a canonical origin would complicate everything.
That being said, if I had to have a theory I would say she's Irish.
That's my old head-canon.
-Yotsuba's head is a four-leaf clover
-Green is a dominant color in the covers
-There are terrorist attacks in Ireland even today, would explain why she thinks fireworks are "the enemy"
-She was born in an island
-Koiwai knows English, and although he may know other languages, we know for sure he speaks English and we have no confirmation that he knows KoreanPost too long. Click here to view the full text.