Mikio Itoo, born in Yokohama, Kanagawa Prefecture on March 26, 1973, is a manga writer for the magazine Weekly Shonen Jump.
An assistant for writer Nobuhiro Watsuki alongside One Piece writer Eiichiro Oda, his three most notable series in the magazine include Normandy Secret Club (ノルマンディーひみつ倶楽部 Norumandei Himitsu Kurabu?), Granada -Ultimate Science Explorers- (グラナダ -究極科学探検隊- Granada -Kyuukoku Kagaku Tankentai-?) and Mysterious Murasame-kun (謎の村雨くん Nazo no Murasame-kun?).
Within the One Piece universe, Mikio Itoo (ミキオイトゥー Mikio Itū?) is also known as a secret gag character printed on various bounty posters through certain early areas of East Blue. Depicted as a smiling man with a gun in his hand, his bounty is known as 1,000,000 yen. Since the currency of the One Piece universe is the Belly, it is unknown how much this bounty is really worth in this world. His name is also written on the grog bottle Shanks offers to Higuma in chapter 1. Itoo appeared as a joke character in two other series at the same time: his master Nobuhiro Watsuki's Rurouni Kenshin and fellow assistant Hiroyuki Takei's series Butsu Zone.