Japanese dwarf flying squirrel, Pteromys momonga
These squirrels are native to the sub-alpine forests of Japan, and are fairly widespread on the islands of Honshu, Shikoku, and Kyushu, though they aren’t often spotted as they live at high elevations. They are nocturnal and rest during the day in cavities in trees. They eat seeds, fruit, tree leaves, buds and bark and feeds while hanging from twigs. They will also forage on the ground. Like other flying squirrel species, they possess a skin membrane stretched between its front and hind legs— called a patagium—which allows them to glide from tree to tree. Their tails help to stabilize them mid-glide.
Interestingly, these squirrels are more closely related to the Siberian flying squirrel (they belong to the same genus) than to their neighbor, the Japanese giant flying squirrel; it is in fact suggested that the Siberian squirrels derived from the Japanese dwarf species.(x)(x)(x)