[Machine Translation] Zechs, a Japanese who has been reincarnated as a countess in an RPG romance game, laments the future of his young sister Karon. Kalon, a villainous daughter, falls to the temptation of the Demon King and is sure to die in every route. -Such an adorable little sister will die an untimely death. There is no way I can allow that to happen! In order to change her fate, Zechs decides to raise Kalon correctly. Zechs, who had an aptitude for unattributed magic and was despised as incompetent, uses his knowledge from his previous life to develop new formulas one after another in order to protect Kalon! He gains uncommon power and teaches Kalon how to use magic correctly. He also detects a spy from the royal court who is after Kalon, prevents Kalon from falling into the darkness by loving him, and dispels any concerns he may have...! If I could be of help to you, my brother, I would love to be of service to you! I'm so cute, my little sister is so cute! The world's most powerful brother loves the cutest little sister! The world's strongest brother tries to avert the ruin of the most lovely sister in this heartwarming fantasy!