What can I say about Usagi Yojimbo that will do it Justice? When I was a teenager (back in the 90's) I tried to read this story of the "Ronin Rabbit" because there was a loose affiliation with the Teenage Mutant Ninja Turtles. However, I really didn't understand the complexity, history, and beauty of the story telling. At that age storytelling was lost on me; I wanted dark superheroes and vigilantes then. I just couldn't get into it then.
Now that I'm 37 I realize Sakai's work was just too sophisticated for my pubescent mind with its short attention span. I'm not some fan boy, nor am I an expert in such matters, I am a librarian and I know what I've read and liked. There are few comic/graphic novel works that I consider grand and epic. First I would be Bone (Jeff Smith), second Maus (Art Spiegelman), and third I would have to include the saga of Usagi Yojimbo.
In brief, Usagi is set in feudalistic Japan of the 16th century where various lords fight for land and power. These lords employ samurai, ninja, and various other soldier types to fight for them. When Usagi loses his master, instead of hiring himself out to the highest bidder he roams the country as a ronin looking for inner peace and harmony, and along the way protecting poor farmers and tradesman from thugs, corrupt officials, and greedy businessmen. Usagi isn't looking for trouble, but Sakai knows that it would be a slow story if it did not find him anyway.
This book could have been rendered using human characters, but like Spiegelman he decided on anthropomorphic characters. While Maus was non-fiction and biographical, and Usagi is fiction, the use of animal characters helps readers detach ever so slightly from the content so that they can handle the inherent violence in the time period while still understanding it.
For parents who may be interested, as it is set in feudal Japan there is violence, in addition you will find religious/spiritual notes that once again are inherent in the place and the time.
I really enjoyed this book.