Game Kaishi Mae ni Shinu Mobu Akuyaku Ouji ni Tensei shita Ore: Oshi Heroine no Imouto to Shiawase ni Naru tame ni Saijaku Mahou "Yamiba" o Kajou na Doryoku de Kiwamenuitara, Saikyou no Bukkoware Seinou to natteita Ken
Game Kaishi Mae ni Shinu Mob Akuyaku Ouji ni Tensei Shita Ore ~Oshi Heroine no Imouto to Shiawase ni Naru Tame ni Saijaku Mahou [Dark Edge] wo Kajou na Doryoku de Kiwamenuitara Saikyou no Bukkoware Seinou to Kashiteita Ken~ / Reborn as the Mob Villain Prince Destined to Die Before the Game Begins: I Turned My Weakest Magic [Dark Edge] Into the Most Broken Skill Through Sheer Effort / ゲーム開始前に死ぬモブ悪役皇子に転生した俺 ～推しヒロインの妹と幸せになるために最弱魔法【闇刃】を過剰な努力で極め抜いたら、最強のぶっ壊れ性能と化していた件～
Luke is reincarnated as a minor prince in a game he played in his past life, where his beloved younger sister Diana is destined to die after falling into darkness. Determined to break that fate, Luke works toward becoming the strongest so he can protect Diana. His efforts begin when he is still a baby, as he sets out to change the future awaiting his little sister.