A Promise

This is the story of Pluto and Aria, Pluto is handicapped and Aria takes care of him. Follow them through depressed, agitated and crazy situations. Both made a promise, because of that promise, they are going on and doing their best. They won't stop, because they have to fulfil the promise. They both promised the same thing, but neither of them knows they have done so. But, what was the promise they promised? It's a fairly simple promise, anyone could say it at any time, but not anyone could keep it.