Okay here's an idea for Trigun:

The desert has always been harsh and unforgiving, permanently unknowable by nature. Even before the legend, there was the man. Long before he became the 60 billion double dollar man, he was a simple wanderer. Finding his brother took a backseat to his exploration of the towns scattered amidst the dunes. This is the story of the humanoid typhoon an the lives he touched. This is The Aria of July.

For D.Grayman:
The world of death was familiar to the bookman. Too often did he have to see others die, but as the old panda told him numerous times, " They are only a small part in history. We are only observers of history." Lavi didn't quite believe those words but he didn't have much of a choice.
Maybe something could happen that he could affect. He hoped...[akuma attacks increase drastically, the Bookmen pair are called into the Black Order to consult]

Any thing you'd like to add or change? Or do you have some ideas you'd like to share? I'm open to it.