Sensei! Bokutachi Ga Sekai Wo Horoboshimasu. 1 (Gangan Comics UP!)

[Machine Translation] A magical school fantasy featuring the most powerful assassin and the most dangerous students! A "teacher" is a holy job to protect and teach students. In this world where people who can use magic and people who cannot use magic are mixed together, a mage, Solo, lives a solitary life. He is also known as "Number Zero," a skilled assassin who always completes his assignments. While he is desperately playing the role of a teacher to accomplish his mission, a transfer student arrives and things take an unexpected turn...

最強の暗殺者×最凶の生徒たちが贈る、魔法学園ファンタジー！『教師』とは、生徒を守り、教え導く聖なる仕事。魔法が使える人間と使えない人間が混在するこの世界で、孤独に生きる一人の魔導士・ソロ。受けた依頼は必ず完遂するという凄腕の殺し屋・No．0（ナンバーゼロ）という異名も持つ彼は、とある任務の一件で魔法学校で教師をすることになりますが、そこで担任することになったのは、学年の落ちこぼれが集まる2年D組。任務遂行のために必死に教師を演じている最中、そこに転校生がやってきて事態は思わぬ方向に…。