Eien no With is the story of a young girl who volunteers to raise a dog for a year until it's old enough to be trained as a seeing eye dog.
I bawled through the entire first chapter, but was disappointed with the latter two. I attribute this to the time-skip: I don't find teenage (or adults who act like teenage) characters as sympathetic/interesting as children, and a lot of teenage emotional drama comes across as too angsty. The art style also changed dramatically after the first chapter, which may have contributed to this (the new art style is more generic).
Anyway. If you love animals and are looking to cry your eyes out, Eien no With is superb. The first chapter easily rates 9/10, and people who grew up with dogs and have a very strong connection to them will probably love the latter chapters as well.