Yotsuba is depicted as an energetic five-year-old girl with a child’s wonder towards even the most unremarkable of new discoveries. She is shown finding enjoyment in nearly everything, and her constant enthusiasm is infectious. Before moving to their present house, she and Koiwai used to reside with his mother, and before that on an island that is, according to Yotsuba, located “to the left”. Almost nothing is known about her biological parentage other than that she was orphaned somewhere outside of Japan and subsequently adopted by Koiwai. Hence, she is often mistaken for a foreigner by people who meet her for the first time. Her excellent skills as a swimmer are admired and even envied by some of the adults. But she is not a gifted artist as she is made to believe; those childish sketches she draws are praised just to prevent hurt feelings.
The name “Yotsuba” (よつば?) can be translated as “four leaved clover,” and is part of the phrase yotsuba no kurōbā (四葉のクローバー, “four-leaf clover”). Her green hair is always styled into four pigtails (even during bedtime), giving her somewhat the appearance of her namesake.