Struggling with a peculiar illness called Chuuni Disease, Shioda Tetsuya tragically passes away, feeling rejected and unfulfilled. Upon rebirth in a new world as a girl named Tilea, he commits to leading a life free of fantasies. Despite finding solace with her caring family, including a sweet little sister, Tilea faces a new challenge. Her sister claims to be one of the Six Demon Generals under Demon King Zorg, posing a grave threat. Determined to cure her sister's Chuuni Disease and unaware of her own extraordinary powers, Tilea embarks on a quest to vanquish the Demon King in this whimsical tale of misunderstandings and unlikely heroism.