Mushoku Tensei: Isekai Ittara Honki Dasu

An unnamed 34-year-old Japanese NEET is evicted from his home following his parents' death. Upon some self-introspection, he concludes that his life was ultimately pointless. He intercepts a speeding truck heading towards a group of teenagers in an attempt to do something meaningful for once in his life and manages to pull one of them out of harm's way before dying. Awakening in a baby's body, he realizes he has been reincarnated in a world of sword and sorcery. He resolves to become successful in his new life, discarding his past identity for his new life as Rudeus Greyrat. Due to inherited affinity and early training, Rudeus becomes highly skilled at magic. During his childhood, he becomes a student of demon magician Roxy Migurdia, a friend to demihuman Sylphiette, and magic teacher to noble heiress Eris Boreas Greyrat.