A 34-year-old Japanese NEET is kicked out of his house following the death of his parents. He intercepts a speeding truck heading towards a group of teenagers and pulls one of them out of the way before dying. Awakening in a baby’s body, he realizes he has been reincarnated in a world of sword and sorcery.
While initially indulging in his perversion, he resolves to become successful in his new life, discarding his past identity for his new life as Rudeus Greyrat. Due to his genetic factor and early training, Rudeus becomes highly skilled at magic. During his childhood, he becomes a student of Roxy Migurdia, friend to Sylphiette, and teacher to Eris Boreas Greyrat.
Shortly after, a teleportation catastrophe scatters many people around the world, and Rudeus resolves to escort Eris home. During his journey, Rudeus receives advice from the mysterious Human-God and befriends Ruijerd Supardia. Successfully escorting Eris home, a misunderstanding with her leaves Rudeus heartbroken.