At the beginning of the series, Hikaru is a sixth grader in elementary school. An important factor in the development of Hikaru's passion for Go is an encounter early on in which Hikaru becomes the rival of Go prodigy Akira Toya. At first, he thinks that Go is just for old folks and he is annoyed at Sai's demand to play, but little by little his passion for Go increases as he plays more and more.Hikaru is often portrayed wearing clothing having the numeral "5". Part of his strength is his ability to read far into the game very fast, and to make seemingly stupid moves, which, in fact, lure the opponent to playing what looks like the obviously correct move, which Hikaru then uses against them.
Source from Wikipeida