Nasu Kinoko (奈須 きのこ, real name Nasu Kunihiro 奈須国広) (born 28 November 1973) is a Japanese author, best known for writing the visual novels Tsukihime and Fate/stay night. Renowned for a unique style of storytelling and prose, Nasu is amongst the most prominent visual novelists in Japan.
For Danbooru purposes, this tag is referring to the Toad-like artist self-insert.