Overflowing with energy and a bright smile! Five-year-old Yotsuba is beyond just "innocent"—she is the protagonist of this story. Whether she's wandering outside on a grand adventure only to return with a straight face, or visiting the Ayase family next door and causing a minor incident, she turns everything into a game. Her Daddy calls her "invincible."

The head of the Koiwai household, who returned to his old town bringing along Yotsuba, whom he found on a southern island. As a translator, he spends most of his day cooped up at home. Perhaps because of this, his parenting style is quite laissez-faire. He is a guardian who watches over Yotsuba's daily antics with a gentle laugh (and sometimes joins in the fun). However, he is surprisingly reliable and knows when to be firm. Early 30s.

The eldest daughter of the Ayase family and a university student. With long, waist-length hair and a frank personality, Jumbo fell in love with her the day they met. She is quite a prankster, stealing strawberries from other people's cakes or joking "Who are you?" to her own father. She dotes on Yotsuba, calling her "like a monkey." 20 years old.

The second daughter of the Ayase family, a high school student. She is the most responsible of the three sisters, teaching Daddy how to put out the trash and babysitting Yotsuba. Her mother says, "I'm so glad I gave birth to Fuuka." Perhaps because of this, she serves as the student council vice president. She recently had her heart broken because the boy she liked had a girlfriend. Yotsuba sometimes tells her she has thick legs. 17 years old.

The third daughter of the Ayase family, an elementary school student. Being closest in age, she often plays with Yotsuba. She is very girly, naming her favorite teddy bear "Julieta," but on the other hand, she worries about global warming and finishes her summer homework early. She is serious and meticulous. 9 years old.

A large man who frequently visits the Koiwai house. He is an old friend of Daddy's and a great playmate for Yotsuba. He is quite the outdoorsman, building bookshelves and taking everyone fishing or to fireworks festivals. He is currently infatuated with Asagi, the eldest Ayase daughter. He drives a Renault Kangoo and his family runs a flower shop. Real name: Takashi Takeda. Early 30s.

Daddy's troublesome friend, or rather, a junior colleague he's stuck with. He has many behavioral issues, like not helping with the move (because it was too hot) and eating cup ramen at other people's houses to save money. Consequently, Yotsuba strangely dislikes him. He is surprisingly prone to loneliness. He is an office worker. Real name: Yasuda. Early 20s.

Ena's friend who visits the Ayase house frequently to work on summer projects or copy homework. Her fashion is very boyish, leading Jumbo to almost mistake her for a boy. Conversely, she shows a girly side in unexpected ways, like being afraid to gut a fish. 9 years old.