Heroes of Paradise

Two human children -Iza and Yuri- end up falling in an abandoned well which leads to another world, and have to find a way back.

Doing so will not be an easy task, however; as they get used to their surroundings, Chikari -Queen of Demons- decides to use this situation for her own benefit and goals, while the deity known as "The Oracle" is tasked with stopping the Queen.

And thus, the children unwillingly become part of this conflict.