The ability (power) he attained in the other world was "24 hours with no fatigue"!?
"...it really is a bit overwhelming"
Taking the blow for a female high school student who was attacked by a slasher, Kagi Tomonori was killed in an unforeseen accident and the curtains to his life came to a close...or it should have, but when he came too, before his eyes was a beautiful girl who called herself a goddess. The goddess told him that she'd let him reincarnate into another world.
"—In return, I want to use this power to defeat the slasher who will also be reincarnated into the same world"
Yup, the slasher Kizagi Tooru who has started everything was given another chance at life by the power of the evil god.
Tomonori, equipped with the ability "24 hours with no fatigue" applicable in terms of mind and body, followed the slasher into the other world and began his life as the 4th son in a viscount family.
Making the best of his ability "Constant Tirelessness" and striving continuously for 46 hours as a 0-year-old baby Edgar, he was able to polish his skills at a rate impossible for normal people.
Then one day, Edgar's father who was working as a commanding officer in a fortress received onslaught from an enemy organisation called 'Black Wolf's Fang' triggering an encounter between Edgar and the enemy. This enemy's characteristics happened to resemble Tomonori's bitter enemy—the slasher.....!?