After sacrificing himself to save a high school girl from a slasher, Kagi Tomonori unexpectedly finds himself granted a unique power in the afterlife: 24 hours of tireless energy. Reincarnated by a goddess into a new world, he is tasked with using this power to vanquish the very slasher who took his life. As the 4th son of a noble family, now known as Edgar, Tomonori harnesses his relentless stamina to rapidly develop his skills. However, his past nemesis reemerges in the form of an enemy organization, 'Black Wolf's Fang,' setting the stage for a fateful confrontation that mirrors his previous life's tragic encounter.