Mori no Kuma-san, Toumin-chuu.

Nowa is a bear who lives in the forest. He found a puppy named Airi a few years ago, and is now raising him. When Nowa goes into hibernation for the winter, Airi is still but a pup. But when Nowa wakes up from his hibernation, he finds Airi has grown into an adult dog.

(Source: Anime News Network)

Note: The complete edition with explicit scenes was distributed web via Comic Festa Anime Zone. The censored version was broadcasted on Tokyo MX and BS11.