Kasei is the Japanese word for "Mars," the fourth planet from the Sun in our solar system. It is known for its reddish appearance, which is due to iron oxide, or rust, on its surface. Mars has a thin atmosphere and features such as valleys, deserts, and polar ice caps. In mythology, Kasei is associated with the Roman god of war, Mars. The planet has been a subject of human fascination and exploration, with numerous missions, including rovers like Curiosity and Perseverance, aimed at studying its geology and potential for past life.