Natsume Isaku manga
The story takes place in what seems to be an almost normal 19th century world -- except that two intelligent species appear to be cohabitating, humans and ferrets. We follow the rather brutal arrival of two ferrets airplane adventurers, Andrea and his manservant Elwood, onto an island in the middle of the Amalou river (pronounce Ah-Mah-Loo). There, two small communities of ferrets and humans - or transparents, as they call themselves - live in a forced autarky. Indeed, there appears to be no way off the island... as well as many a mystery waiting to be uncovered. Little do our two gentlemen know that their curiosity will eventually lead them to the edge of the world and beyond, to the Kingdom of the Great Oak where legends take flesh... Now read on!