Kitsune no Sekai

During the Kamakura period, Kyoto was filled with mischievous foxes. They lived happily alongside humans until the huge great war wiped them out, leaving foxes to inhabit all of Kyoto. However a few years after the war, a huge torii gate with a portal appeared. 

The gate crosses over from Feudal Kyoto to Modern.. Allowing foxes the freedom of switching to and from times.