Mushoku Tensei: Isekai Ittara Honki Dasu  

Mushoku Tensei: Jobless Reincarnation, 無職転生~異世界行ったら本気だす~, 無職転生 ～異世界行ったら本気だす～, 无职转生 ~到了异世界就拿出真本事~, เกิดชาตินี้พี่ต้องเทพ

In the afterlife, a 34-year-old man named Rudeus Greyrat is reborn into a world of magic as a newborn baby. He has retained all of his knowledge and experience from his previous life, but also regrets for any mistakes he made. As a genius in the making, he vows to lead a fulfilling life and avoid repeating past errors. Rudeus possesses an immense amount of magical power due to his newborn status and the mind of a grown adult. His parents see him as a prodigy, and he begins studying under powerful warriors such as his father and a mage named Roxy Migurdia in order to hone his talents. Despite his innocent appearance, Rudeus is still an otaku who uses his knowledge to pursue women whom he could not approach in his previous life.

Mushoku Tensei: Isekai Ittara Honki Dasu adapts chapters 1-26 of Yuka Fujikawas manga series and volumes 1-3 of Rifujin na Magonotes light novel series of the same title.