Ken to Maho no Sekai Desuga, Ore no Kikai Heiki wa Kyo mo Muteki Desu. (HJ Bunko) [Light Novel]

[Machine Translation] In a world where people no longer die except from old age, Age is the only boy who can die from injury or disease. Moreover, he was a heretic who could not even use magic, which all human beings could use. Ten years ago, Age acquired a "workshop" capable of creating a wide variety of mechanical weapons, and its manager, a fox-eared girl named Tenko. Chosen to be her master, Agee makes full use of the mechanical weapons of his own making and destroys any and all enemies that stand in his way!

老衰以外では人が死ななくなった世界で唯一、怪我や病で死ぬ可能性がある少年エイジ。しかも彼は全人類が使える魔法すらも扱えない異端者だった。そんなエイジが十年前に手に入れたのは、多種多様な機械兵器の作成が可能な“工房”と、その管理者たる狐耳の少女テンコ。彼女の主に選ばれたエイジは、今日も自作の機械兵器を駆使し、立ちはだかる敵を残らず殲滅する!