Killed while saving a stranger from a traffic collision, a 34-year-old NEET is reincarnated into a world of magic as Rudeus Greyrat, a newborn baby. With knowledge, experience, and regrets from his previous life retained, Rudeus vows to lead a fulfilling life and not repeat his past mistakes. Now gifted with a tremendous amount of magical power as well as the mind of a grown adult, Rudeus is seen as a genius in the making by his new parents. Soon, he finds himself studying under powerful warriors, such as his swordsman father and a mage named Roxy Migurdia—all in order to hone his apparent talents. But despite his innocent exterior, Rudeus is still a perverted otaku, who uses his wealth of knowledge to make moves on women whom he could never make in his previous life. [Written by MAL Rewrite]

Mushoku Tensei: Isekai Ittara Honki Dasu is a web novel that was serialized on Shousetsuka ni Narou website from November 22, 2012, to April 3, 2015. It made repeated appearances on the site's rankings as the most popular work during its serialization. Media Factory published the first volume on January 23, 2014. The series was published in English as Mushoku Tensei: Jobless Reincarnation by Seven Seas Entertainment under the Airship imprint from May 21, 2019, to March 12, 2024, and as deluxe hardcover 3-in-1 omnibus volumes since November 25, 2025. It has also been released in Italian by Dokusho Edizioni since July 26, 2024.