I've seen bits of this anime around, and my friend has a keychain of one of the characters. What is it about? Is there a manga?

Hi Cosmos-Hime! 

answering the second question first, yes, there is most definitely a manga! It's still ongoing, and the latest chapter came out about a week or two ago.

For the first question, it's about a group of people working at the Armed Detective Agency (or ADA for short). Most of the people at the Agency have some sort of supernatural ability, and are fighting against the Port Mafia, which rules the city's underworld. 

It also has a lot of literature references in it, most characters are named after a famous author, and their abilities named after a work of theirs (or a line from said work). I think there are a few that aren't, but a good deal are. 

Also I'm totally curious, which character is the keychain, do you know?

*poke* 

anyone else a fan of this series?