Demon Lord reborn as The Hero's Child

What do you do when the man who murdered you becomes the father who tucks you into bed?​Raizen Kurogane ruled the demon realm through fear, ash, and absolute power. Kings knelt. Armies broke. That is, until humanity’s greatest champion drove a divine blade through his heart and ended his reign for good.​Death should have been the end.​Instead, the former Demon Lord opens his eyes inside the fragile body of a human infant. His devastating magic is sealed. He can barely hold his own head up, let alone take revenge.​And the towering warrior weeping tears of joy while cradling him?​The very Hero who executed him.​“Welcome to the world, Kōya. My son.”​Trapped in mortal flesh, Raizen tells himself this is just an undercover assignment. He will bide his time. He will nurse his strength, slit his killer’s throat in his sleep, and reclaim his blood-drenched throne.​There’s just one terrifying problem:​His new father is an idiot who loves him unconditionally.​The hands that once severed demon heads now clumsily change diapers. The battle cry that rallied kingdoms is now reduced to terrible, off-key lullabies. For the first time in his bloody existence, the monster who conquered the world experiences the one thing he never anticipated: a warm meal, a gentle touch, and a home.​Revenge is easy when you’re facing an enemy. It is impossible when that enemy would gladly burn down the world just to keep you safe.​Then, the dimensional rifts begin to tear open.​The remnants of Raizen's old demonic legion are scouring the realms, leaving ash in their wake as they hunt for their missing sovereign. They don't want peace. They want their Demon Lord back to finish drowning humanity in blood.​To protect the fragile life he swore to destroy, Kōya faces an impossible choice:​Reclaim his throne as the nightmare of his past... or pick up his father's blade and wage war against his own kind.