when was it released?
The series consists of thirteen games. The first "Kingdom Hearts" was announced at E3 in May 2001.
Kingdom Hearts
The first "Kingdom Hearts" was announced at E3 in May 2001. 
what is kingdom hearts? Action role-playing video game
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Kingdom Hearts [SEP] Promotion
The first "Kingdom Hearts" was announced at E3 in May 2001. Initial details were that it would be a collaboration between Square and Disney Interactive, and would feature worlds developed by both companies and Disney characters. New characters were designed by Nomura and include Sora, Riku, Kairi, and the Heartless. On May 14, 2002, a press release announced a list of the English voice actors. The list included Haley Joel Osment, David Gallagher, and Hayden Panettiere as the three new characters introduced into the game. It was also announced that many of the Disney characters would be voiced by the official voice actors from their respective Disney films.