Shiga Kenbyaku

Twin Star Exorcists: Shika Kenbyaku (双星の陰陽師 ―士牙繭闢―) is the second official novel, written by Hajime Tanaka and supervised by Yoshiaki Sukeno.

Extra Manga
This extra is called 士牙繭闢～三色滑稽画之序～, which is also included in the novel.