Yamazaki Susumu begins as a spy for the Shinsengumi but later turns against them. He sports medium-length dark purple hair, with strands long enough to fall over his right shoulder, and light purple eyes. His attire features violet and purple colors, including a jacket with four buttons and sleeves ending at his forearms.

Characterized as supportive and methodical, he approaches Shinsaku Takasugi and Kogoro Katsura after their prison escape, urging them to meet Tokugawa Yoshinobu swiftly. He participates in locating the Chronometer, revealing Tokugawa rescued their captives from the Shinsengumi. He then accompanies Tokugawa, Shinsaku, and Kogoro to track the device. To secure the Chronometer for Kogoro, he assists in confronting Miyamoto Musashi, one of Susanoo's twelve commanders, fighting alongside Shinsaku until Sakamoto Ryouma and Okada Izou arrive as reinforcements.

Later, investigating reports of ghostly fires in Kyoto with Shinsaku and Kogoro, they encounter the Shinsengumi. Yamazaki takes shelter with Ryouma and Izou in a soba shop basement. He subsequently aids in evacuating citizens when the Chronometer causes a burning temple to appear in the city's sky.