Yugi Mutou is the main protagonist of Yu-Gi-Oh! Duel Monsters. At the start of the series, he is a shy boy who is really short for his age, something he always gets teased about in school. For this reason, he was always alone. However, his grandfather gives him the Millennium Puzzle prior to the story's time line and Yugi is told that if he solved it, one wish of his could be granted.
Source from Wikipeida