Stanley's sketchbook, or Ariga's sketchbook in the Japanese version, is a sketchbook belonging to the artist, Art Stanley.
According to Art, the sketchbook is more important than his life, as it contains all of his ideas and designs for comics.
When Art was unable to find out Yuma's weak point, he discovered Shark's. Art claimed every step of the plan was illustrated in his sketchbook. Girag approved the plan and Art vowed to do his best for the glory of the Barian World. During the Duel, before Shark activated "Zeus' Breath", Art revealed that his sister was trapped inside "Castle Artopia" in the kingdom of "Stanleyus". Shark said this was impossible and Art claimed that if Shark defeated him, his comic book world would be destroyed. Art wondered what would become of Rio if that happened, laughing maniacally. Tori asked if there was something they could do to save Rio. Astral responded that the world is Art's creation. Tori, remembering the sketchbook from earlier, suggested that Yuma find it, while adding that the world itself should be drawn from that sketchbook. Yuma thought she may be right, as the sketchbook could have some hints. He, Ray and Astral rushed off to find it, with Yuma vowing to save Rio. When Shark's Life Points fell to 500, Yuma contacted Shark through his Duel Gazer, telling him he found Art's sketchbook at the Comic Book Appreciation Club. Later, Shark was able to defeat Art in a Duel and everything returned to normal.