Steam in 2016, and they describe the story:
In a certain ancient ruin, two doors were discovered, then accidentally opened. Through these doors were two different worlds: the World of the Gods, and the World of Demons. The three worlds from then on out became interconnected, bringing drastic changes to the human world.
The story takes place in an average town in an average country.
Two different families moved in either side of a boy who was living in peace and quiet. These were the families of the King of the Gods and the King of the Demons, the rulers of their respective worlds. Both of these Kings had moved upon the wishes of their daughters, who had been in love with the boy since they were young. Years ago, the two girls met the boy only for a moment and neither of them could forget that fateful encounter as they continued to hold him close in their hearts.