Mitsujiro, a blonde Japanese-American half who came from the United States, is assigned to a high school where her sister Nagisa attends as an English teacher. Mitsujiro and Nagisa's father went to the United States before Nagisa was born, and Nagisa's mother died shortly after moving to the United States. For this reason, Nagisa had a strong complex with English and blonde hair, and was reluctant to call Mitsujiro "an older brother." However, she gradually overcomes the complex through interacting with Mitsujiro and his classmates. Then, in order to find out why his father broke up with Nagisa's mother and went to the United States with Mitsujiro, she left for the United States with Mitsujiro to meet his father.

(Source: Shogakukan, translated)