Yamazaki Sagaru (山崎 退 Yamazaki Sagaru ), formerly nicknamed as Mountain Zaki, is a spy working for the Shinsengumi. He himself confessed that he is "very plain" which helps him in undercover missions. He is known for his love for badminton, often playing or practicing badminton alone instead of working (he is often caught by his Vice-Commander Hijikata Toushirou and is subsequently roughed up as a result). Despite all this, Yamazaki still often at times get ignored and unnoticed. Prior to the Shinsengumi being officially established, he was originally a punk.