Sure, there is a manga for Death Parade. It expands on the story and characters presented in the original concept. The manga offers additional depth and details that fans might appreciate.
I have no clear idea. It could depend on the creator's plans or the popularity of the series. Try searching manga-specific websites or communities for accurate information.
It could be an evil shinobi from Naruto's world who has also ended up in the Death Parade world and is trying to corrupt the system. He wants to ensure that all the souls are sent to the void or something worse, just for his own amusement or power - hungry desires.
Perhaps Naruto enters the Death Parade world in search of a lost comrade. He teams up with the arbiters, reluctantly at first, when he realizes that they have some knowledge about where his friend might be. Along the way, he shows them the power of friendship and loyalty that he has learned in the Naruto universe, and they in turn show him the complex nature of the afterlife in the Death Parade world.
Sure. The manga goes beyond what's shown in the anime and gives you a richer perspective of the universe it creates. You'll learn about hidden aspects and get a more elaborate exploration of its themes and settings.
Definitely. 'The Black Parade' has many characteristics of a dystopian story. It may feature a broken social structure, limited freedoms, and a bleak future for its characters.