Yotsuba Koiwai is a cute, fun loving girl who is always getting into mischief.
Yotsuba Koiwai is..... well.... a typical 5 year old, energetic, enthusiastic, amazed by everything. In volume one Yotsuba's father is noted as saying "She can find happiness in anything, nothing in this world can get her down". This just reinstates that fact that she is a very happy girl. Yotsuba is also very forgetful, so much so that she has even forgotten her age a one point. Yotsuba is also noted as being a foreigner by the other people in the manga. When she first moves into her new house she is still confused by the moving process and tells Fuka that her house is "Way over there" while pointing to the left. Also Yotsuba does not know where she comes from but when people ask her, her response is "To the left".
Come on. How can you resist that face?!
For some reason Yotsuba is scared of all things that resemble a bullseye.... this is never explained but hilarious events ensue because of this.