Well, back when we were still traveling the Singularities made by the Grand Caster, wherever we went, there was a huge ring of light in the sky. It would always remind us that humanity was still on the verge of extinction.

And Chaldea's so high up in the mountains where there's always a blizzard. I've only been able to see the sky from there once. [ it's still a somewhat overwhelming memory for him, mixed with happiness and accomplishment but also of sadness and regret for a certain Doctor ] Seeing just the blue sky with only clouds and the sun in it... it's a relief.