Most isekai manga forget about these moments. It's all about the glory and the OPness, and when it has to come down to pulling some heartstrings, it's usually just some ruined village filled with no one, or maybe a single person who died.
This is war. Lots of people die, and even if we never knew most of them, this shows that Ars did, personally. That counts for a lot more. And writing letters helps him cope with it. I was afraid they were going to portray him as self destructive or needlessly isolating himself, but this is good.