Complex sentence: She has been taking care of Koichi at home while Koichi's dad has been away, and at the beginning of the story, gives him advice about Yomiyama Middle School through a series of "rules".
Split into simpler sentences: She has been taking care of Koichi at home while Koichi's dad has been away. At the beginning of the story, she gives him advice about Yomiyama Middle School through a series of "rules".