A country of youkai on the other side of the human world. Tengu Tenmaru, the only son of Tengu Daio, the ruler of this country, invades "Oreyama", which is forbidden to enter, on the night of the annual specter festival, accompanied by Kuro, the child glass tengu. A cute girl youkai appears there. In fact, this mountain is a prison of a monster country where 108 evil monsters are confined, and a girl monster is one of them. Tenmaru is deceived by a girl youkai and breaks the seal of the evil youkai. One hundred and eight monsters escaped to the human world after having a rampage in the festival of monsters. Angered by Tenmaru's mischief, Tengu Daio broke Tenmaru's nose and ordered him to exterminate the 108 monsters. He gave Tenmaru the seven tools to exterminate youkai, ordered Kuro to accompany him, and set Tenmaru on his journey. Thus began the battle between Tenmaru and the 108 monsters led by the Great Demon King Bemular.