Donyatsu(2011)

Donyatsu

Summer, 20XX. A chocolate doughnut-shaped creature that resembles a cat, Donyatsu, walks amongst the rubble of a fallen civilization. He and his friends experience a carefree life in this strange world. But the question remains—where have the humans gone? And what caused this post-apocalyptic situation? An easy-going sci-fi adventure that slowly unravels these mysteries beings!

(Source: Manga Up!)