This manga has been one of the only ones to make me shed tears for the characters. It's surprising how well built the relationships between the characters are; the passage of time is portrayed as virtually non-existent (from the perspective of the elf's lifespan) but it also conveys just how much time truly passes during and between chapters.
If I had to describe what this manga truly wants to portray, I'd say it portrays the way we truly don't think much of things that have happened in our life, and when we do those times have already gone by, and are just memories we have to hold dear in our hearts (whether bitter or sweet) and keep living in the present.
This one is, truly, a gem.