Congratss that's a really big accomplishment!
I'm kinda tired of copy pasting the summary soo I'll explain it like:
The tale of two groups of brothers, the first group living in the "original" world whereas the other group lives in the mirror world, thus being the parallel selves of the former. They represent the sides of the other group that lie hidden within them, it's basically them being an expression of the effects of the first group enduring hard to cope events.
Both sides are explained according to where the story is, the first chapters mostly deal with the original group and later, how their hardships are then expressed through the other group of brothers.
One of the main characters deals with a lot of issues like stress, inability to eat, insomnia and a crushing solitude as he feels far away from his brothers to which he believes failed to protect. He is not open about his feelings, but he cares about his siblings a lot. (Kinda tsundere but without the exaggeration often found in anime)
His mirror self deals with narcolepsy, emotional eating and frustration over needing to be looked after despite his desperate need to take care of the other two like a loving brother.
I always show the cover so I'll share a picture of two of the characters instead xD