Natsuha Sawai is a central character in the visual novel 'Monobeno.' She is the younger sister of the protagonist, Tooru Sawai. Natsuha is depicted as a cheerful and energetic girl who deeply loves her brother. Her character is pivotal to the story, as her mysterious illness and its supernatural implications drive the narrative forward. Natsuha's innocence and vulnerability contrast with the dark themes of the story, emphasizing the protagonist's struggle to protect her and uncover the secrets of Monobeno. Her relationship with Tooru adds emotional depth to the series.