Sousou no Frieren: meaning of nonsensical journey

I want some heal from MADE IN ABYSS so the Iyashikei tag is the way. and this anime is on the top right now!.
tags Adventure, Drama, Fantasy
Let's go see it at
www.livechart.me/anime/11376/...
0:00 Introduction
0:27 Story
1:14 Good
Sunny · Yorushika (opening2)
• Sunny
bliss · milet (original sound track)
• bliss
1:58 Bad
2:15 Conclusion