Mariko Hirose is a central character in the anime series 'Green.' She is a high school student with a passion for environmental science and sustainability. Mariko is portrayed as intelligent, compassionate, and driven, often taking the lead in school projects focused on eco-friendliness. Her role in the series involves rallying her classmates and community to join her in various environmental initiatives, making her a pivotal figure in promoting change and awareness. Her journey throughout the series highlights her growth as a leader and her dedication to making the world a greener place.