Frieren - Remnants of the departed #1

"Shaken by how little she knew them, Frieren is now determined to learn about life from the human perspective. Agreeing to mentor a war orphan entrusted by her old comrade, she embarks on a journey of discovery…
---
Fifty years after the Demon Lord’s defeat, Frieren and her heroic party are reunited. For an almost immortal elf like her, it seemed like only yesterday, but her now-elderly human friends are leaving the world one by one.
Before his death, Heiter manages to foist a young human apprentice called Fern onto Frieren. Driven by the elf’s passion for collecting a myriad of magic spells, the pair embarks on a seemingly aimless journey, revisiting the places that the heroes of yore had visited. Along their travels, Frieren slowly confronts her regrets of missed opportunities to form deeper bonds with her now-deceased comrades."