Once, transfer to Hyakkau academy pretty to Mary Saotoma. The newcomer has impudent and independent temper therefore it is difficult for it to find a common language with people around. Trying to adapt somewhat quicker to new realities, the main character learned that in educational institution the special system of gamblings works. From the first day she begins to be interested in this phenomenon. Pretty quickly she managed to become one of the main team players. The little girl won great popularity among the age-mates admiring it an improbable game. 

Mary's passion to hobby where on a game there were high rates is shared by friends schoolmates Ryota and Yumeko. The last is a mysterious young person. Can seem that she is modesty, but when Yume sits down to a game table, her eyes for some reason become red, demonic. In one of days Yumeko lost and is forced to begin the way as "pet", the got beaten person. The debtor having an opportunity to give loss does not want it to do, she throws down a challenge to the president of the academic council. Ryota, unlike friends - very mediocre player who owes Saotoma the large sum...