I'll write an actual review but first I just want to say what moved me to comment in the first place: Framing Story Hedwig talks like a Dark Souls NPC, and I think that's wonderful.
The writing, backgrounds and music come together to create a really great atmosphere. The character designs do amazing work to visually distinguish a cast of characters that necessarily all wear the same clothes, and their personalities are just as distinct and vividly rendered. I'm excited to learn more about each of them!
Hedwig's ultra-religious perspective makes her a fascinating protagonist, especially seeing her immediately run up against the reality of the normal nuns, who (gasp) curse, and complain about the Superior's singing, and don't follow a strict and extensive prayer schedule. It's fascinating both cause that's not a typical perspective in a story and cause I remember, long ago, being a very religious little child who was scandalized by all sorts of normal stuff.
This is clearly a serious story overall, but complemented by a great sense of humor that runs throughout. The lunch scene was a pleasure to read.
I don't have a good way to conclude this, except to say I'm looking forward to the full volume one!