One of Shobu's close friends. Even though he is an expert at the rules of "Duel Masters," he's a terrible duelist, often going without a single win during a tournament. He's often seen with his portable laptop to keep track of important duels. As a running joke, he is often accidentally knocked far into the air--in one instance (which only occurs in the English "dub"), he was sent flying into space (against a live-action backdrop) and crashed into a space station. He has almost every card ever released (since his father Maruo [丸雄; Maruo] owns a card shop) but cannot correctly use the cards. His correct surname is "Kadoko" (かどこ=角古) NOT "Kadoka" (かどか)wich is actually japanese female given name. When spoken in Japanese (i.e., putting the last name before the given name), his name is actually a pun on (カードコレクター, Kādo Korekutā?), which is a Japanese katakana transliteration of the English phrase "card collector". In the Japanese manga, his "otakudom" in card collecting often helps Shoubu, or at least give him a clue or a hint towards winning a duel.

(Source: Wikipedia)