Takaido is a character in the Yu-Gi-Oh! manga. He is unnamed in the manga, but called Takaido in the Japanese anime and Sid in the English anime.
In the Duelist Kingdom tournament, they meet up Bandit Keith, who agrees coach them through the tournament so all four of them will advance to Pegasus' castle. While helping them win Duels the first day of the tournament, Keith secretly intends to use them for their Star Chips.
When Keith finds out about Yugi Mutou, Katsuya Jonouchi, and the rest of the gang, they believe they will get in their way, and seek to eliminate them. When Jonouchi runs away from the group to urinate, Satake beats him unconscious and he wakes up in cave with a Battle Box, complete with a Graveyard Field. Ghost Kozuka challenges Jonouchi to a Duel that he tricks him into thinking he must accept; however, Jonouchi wins the Duel.
Bandit Keith then locks the gang in, and turns on his own companions. Since Satake and Takaido had five Star Chips each, Bandit Keith takes them from them (along with a Dueling Gauntlet) after beating up Kozuka for losing. With those ten Star Chips, he becomes the first to qualify for the finals.