Story- I think one of the reasons why I loved growing up with Tegami Bachi was because of its world building. We have a world shrouded in darkness with an artificial sun to bring light to the world of Amberground. Then we have three districts of people, being those from Yodaka, Yusari, and also Akatsuki. Within this world are the Letter Bees, letter carriers responsible for carrying the hearts of the people from place to place while dealing with the dangers of Gaichuu, these insect armor monsters that attack people for their heart. But what exactly is heart? I think heart is what makes a person who they are, their own identity. But if you take that away then they have nothing, resulting in death. The story begins when Gauche Suede, a letter bee, is delivering a boy named Lag Seeing to his destination. Lag meeting this letter bee is huge significance to the story, as it drives Lag Seeing to become a letter bee himself. When that happens the story really begins to pick up. The beginning is a bit slow, but as long as it serves to develop the story then I don't really mind. You never know what's going to happen next, which is part of the series' charm.
Art- The art itself for the series is really gorgeous, the way the line design for the characters is drawn beautifully, and looks even better in color, which may explain why Tegami Bachi got so many color covers during its run. The desolation and ruin of Amberground is drawn very well too, showing how the world has fallen into a shell of itself.
Characters- Let's start with Lag Seeing, the main character. Lag is easily one of the most empathetic protagonsts I have see in anime and manga for years, but I consider that a good thing. We have a character who care about others enough to get involve, even if it means endangering himself compared to some of the letter bees. But its that kindness that makes him so radiant. Taking a note from the author, I too think its alright for a guy to cry for the right reasons, which falls in line with Lag's character. Zazie was definitely one of my favorite characters, even moreso later on with his backstory. With a variety of characters to choose from I'd say Asada is pretty good when it comes to writing characters, with what shapes them and what motivates them.
Overall, without including my nostalgia too much, I can easily declare that Tegami Bachi is one of the better Shonen series to get into. Along with marginalization, there are a lot of themes to think about with this series. Along with the gorgeous artstyle, the author was pretty clear with his goal for the main characters and he acomplishes it. I think the series ends on a happy note, and wraps up all the loose ends. Asada is easily one of my favorite authors now.