http://www.onemanga.com/Liar_Game/
Nao Kanzaki, an honest college student, receives 100 million yen one day, along with a card saying that she has been chosen to participate in the "Liar Game". In order to win the game, she must trick other players into giving her their 100 million yen while her opponents are left in debt.
A really awesome logistical series- not quite a mystery, but with a lot of deducing and stuff going on.
Anyone else read this series?