Koyomi Yamanaka is a fictional character from the popular visual novel series Kagetsu Tohya and Tsukihime. He is known for his role as a high school student who becomes involved in supernatural events and encounters various characters with unique abilities. Koyomi is characterized by his strong sense of justice and determination to protect those he cares about. Throughout the series, he navigates complex relationships and challenges, often showcasing his growth and resilience in the face of adversity.