在一个被称作『逆JAPAN』的空间，每隔44年就会打开一次“妖逆门”释放大量妖怪，一位神秘的少年多闻三志郎将在这里展开异想天开的奇异冒险。

Sanshiro's chances of having an adventure are slim to none in his tiny island hometown, until the day a mysterious stranger invites him to play a game... Without warning, Sanshiro is taken to a backwards universe to play BakéGyamon—a game pitting monsters against monsters. Along the way he meets other players who have a particular reason for being there—to obtain the wish that is granted to the winner. But how far can Sanshiro get when the monsters he's been paired with are a bunch of little mud balls?

小学5年生の多聞三志郎が家出同然の形で始めた一人旅。だがその途中、奇妙な男フエに見込まれ、日本にそっくりだけと違う空間逆日本へ連れて行かれてしまう。そこで知った妖怪たちの危機。妖怪を救うため、多聞三志郎は最後まで勝ち残れば何でも願いを叶えて貰えるげぇむ妖逆門の予選へ向かうのだった。