Mai-chan no Oneesan Shiiku Gohan.

One day, the fifth-grader Mai found a beautiful blonde-haired high-school girl passed out from hunger in front of Mai's rural home. But despite her mature looks, the girl doesn't know how to cook or take care of herself. So Mai takes it upon herself to cook and care for her new neighbor like a mother, or like adopting a pet?

(Source: Japanese Publisher, translated)