This is another Shonen named Tegami Bachi or Letter Bee
here are the famous main characters:
the stories about this kid, Lag, who becomes a Latter Bee and then meets this strange girl who he names Niche. They go on huge adventures.
I'm reading it as a Manga but it now has its own Anime show.
Its one of my Favorite Animes!! 
This is the guy who inspired Lag to be a Letter Bee, Gauche. Lag while on his travels is looking for him.
Lags main reason for beeing a Letter Bee is to find his mother who was taken away.
This is Niche. A strange girl that Lag met whilehe was in town. Apparently she was a letter so he was going to deliever her. But she chose to be his "Dingo", a pet companion.
And lastly but certenly not least! This is Lag Seeing. A boy who was delievered as a letter by Gauche to his Auntie. When he got older he chose to become a Letter Bee because he wanted to find his mother who was taken away from him.
well there's pretty much the show in a nut shell.
