Even if you don't have a lot of time on your hands, a oneshot is something that can be read fairly quickly, so if you're having doubts on whether to read this or not it really won't take out much of your day so I strongly recommend at least trying it.

Story: 10/10
Generally with one shots they aren't able to get a solid story with well rounded characters and information out in a very short time frame, however, this manga manages. We quickly understand the situation the world is facing, and the struggles the heroes are experiencing. The story dives into ways that are unexpected and leaves you with a sense of sadness.

Art: 9/10
You can tell a lot of time went into the artwork by how beautiful it is, especially the pages that have been coloured.
The art is more than your average manga, thought was definitely put into the environment and characters and the shading is phenomenal.

Characters: 9/10
For having such a short time-frame to tell the story we witness a lot of development between the characters, and we learn a lot about the type of people that they are.

Enjoyment: 9/10
I definitely did not regret reading this, and I'm very glad I gave it a chance.
Hopefully you enjoy picking this up as much as I did.