Who Are They Gonna Tell Them?

The anime and manga series Masanori takes place in an unnamed fictional world with a variety of different countries and locations.

Creation and conception
Yunokawa Tetsuya's reasoning for placing Masanori in a different world was that he couldn't simply picture the events of the mythology unfolding in a modern setting. Tetsuya also felt that he could escape limits by creating his world for the series as then the only boundaries would be those set up by him. After making his decision to create a different world, Tetsuya then decided that the world and it's history would be based mostly off Japanese mythology.

History
The history of the world mirrors that of the creation of the Japanese archipelago in Japanese mythology.