Card no Ousama

From CMX:
"Chaos" is a trading card game that is very popular at Manami's school. Trying to learn more about it herself, she purchases a beginner's set, only to discover that it contains "Sahgan, The Mighty Sorcerer," the rarest card in the game. Now every other player is out to win the card from her. But Sahgan himself begins to visit Manami in her dreams, offering her advice on how to win.