○-hon no Juunin

This 4-koma style manga follows the life of a girl named Noriko. Noriko and her big brother live together, with no parents, in an apartment. Her big brother writes illustrated children's stories for a living, and his work is managed by an impressive, skilled, pretty boss named Yoko, who Noriko has always admired. At school, Noriko's teacher is a friendly, laid-back woman that the students call "Sanae-chan." Noriko's friends include Mika and an athletic half-Japanese girl who sometimes says the strangest things. These are the elements that make up the everyday life of Noriko!

(Source: MangaHelpers)