Soushi Yukimi is a fifth-grade student at Oedo Elementary School and one of the three modern descendants of the Shinsengumi. He uncovers his ancestral connection to Okita Sōji, reflected in his naming, alongside classmates Isami Hanaoka and Toshi Tsukikage after discovering artifacts in Isami's basement. These artifacts include a message urging them to combat the Kurotengu organization.

Soushi exhibits a suave and flirtatious personality, frequently presenting red roses to females he finds attractive. Despite his youth, he confidently attempts to charm women significantly older than himself, such as librarians, though his friends often intervene. Multiple female classmates, including Mayuko Kiyokawa and Izumi Maki, develop affections for him.

His combat role centers on the Dragon Fangs, ancestral artifacts combining to form a luminous bow. This weapon fires energy arrows channeling spiritual energy derived from Luminotite. Soushi's fighting style emphasizes precision and ranged attacks, aligning with his designation as a "Master Archer."

Within the trio, Soushi represents the "nice" aspect, contrasting with Toshi's "mean" demeanor while Isami provides balance. They share a close friendship, collaborating to investigate mysteries and thwart the Kurotengu organization's schemes amidst their school responsibilities. Soushi occasionally draws advice for peers from his romantic experiences.