Mushoku Tensei: This Time, I’ll Be by Your Side

At the end of a tragedy came the Man-God's mocking laughter. Roxy died of illness, Sylphie met a gruesome end, and Rudeus, having lost everything, died in despair. For some unknown reason, Rudeus returned to the moment of his birth. He swore to make up for the regrets of his previous life. But he soon discovered that the world had changed: Roxy, who was supposed to become his teacher, had vanished, and the red-haired girl had become someone he didn't recognize. "With only Sylphie left, at least let me protect her." But Sylphie kept acting strangely, until one day an unexpected incident occurred... "Sylphie, I never taught you voiceless magic." This is a story focused on Sylphie alone. Rudeus dies shortly after Sylphie does. Plenty of sweetness, little angst. Come give it a read.