The Victim Boy is Revived as a Demon Slayer in Another World

Japanese Name: Chikyū kara no gisei-sha ga dēmonsureiyā to shite betsu no sekai kara fukkatsu shitara (地球からの犠牲者がデーモンスレイヤーとして別の世界から復活したら)
English Name: Once a Victim from Earth is Resurrected from Another World as a Demon Slayer

Tomoya Ueda, an eight-year-old boy of the affluent Ueda family, had a fascination with kings and princes from his favourite TV shows, and had dreams of becoming one. However, due to this, his life quickly spiraled upside down when one of his former friends exposed his secrets, causing him to be the subject of such greater derision and mockery from his other friends. With that, he became estranged from society, in hopes of having "fun" without the biting reality of the outside world.

His last day in the world of the living was when he fell down after saving his real childhood friend Ayane from falling down into a riverbank, causing him to be killed in an instant. As he woke up in Limbo, he later greeted the soul reaper of the Underworld, who thinks Tomoya is a special case, who can make his wish come true.

He was given a second life, but not before problems persisted! The soul reaper himself made a master-slave contract with the soul of Tomoya, and his resurrection spell is a massive failure, causing most of Tomoya's past memories to be included! He is reborn as a newborn baby and mentally curses Meralte, the former identity of Death, for his idiocy and utter incompetence.