Aria the Scarlet Ammo (Hidan no Aria) 11 (MF Bunko J) [Light Novel]

[Machine Translation] Tokyo Butei High School is a special school for training detectives who use military force, known as "Butei". Kinji Toyama, an ordinary person, is chosen as the partner of Aria, a super-elite and the strongest S-ranked detective in the Assault Department. Aria and Kinji find themselves in a battle between the "Division" and the "Family". In the meantime, Kinji is living together with Kaname, his self-proclaimed "sister". The Baskerville girls, unable to stand idly by in this situation, challenge Kaname to a "duel". Kinji ends up on Kaname's side in the duel...? Baskerville becomes Kinji's enemy! This is the 11th volume of a large scale action and romantic comedy series that has also been made into a TV anime.

東京武偵高校、そこは武力を行使する探偵―通称『武偵』を育成する特殊な学校。強襲科の超エリートでSランクの最強武偵・アリアのパートナーに選ばれてしまった(普段は)ただの一般人・遠山キンジ。『師団』と『眷属』の争いに身を投じたアリアとキンジ。その最中、キンジは自称「妹」のかなめと同居生活中だ。この事態に黙ってはいられないバスカービル女子の面々が、かなめに「決闘」を申し込む。キンジはその決闘でかなめ側に付くことになり...?バスカービルがキンジの敵に!?TVアニメ化もされた、大スケールアクション&ラブコメディー第11弾。