The story takes place in Tokyo Butei High School, a special school where armed detectives — "Butei" — are trained to use weapons. Kinji Tooyama is a second-year-student who has a special ability, but he keeps it a secret to maintain an ordinary, peaceful life. However, when he gets caught in a bombing on the way to school, he encounters H. Aria Kanzaki, the most powerful S-Rank Butei student in Assault Studies.
I love to watch Hidan no aria coz it's involved guns & fighting. I love how the song mixes with gun shots and sword slashing in beginning XD. When i watch this anime from 1-12 episode. Hey not bad.It wont make me feel bored.I would say this is the best animes that I've seen:) must watch this.