tl:dr version:
The Pinnacle of the twitch shooter genre for me personally. 10/10

Katana Zero is an amazing piece of software.
I originally picked this up to waste 2 hours of my life with a random devolver game.
What I got was a masterpiece which has surprising depth in both gameplay and narrative.
It is a short game, which could be a deal breaker for some. Let it be known that it has great replay value,
due to the fact that it has branching story paths and extra content hidden.
My first playthrough clocked in at around 2 - 3 hours. I 100%ed it in 8 hours.
52 more playing hours have occurred thus far.
Aditionally it is a great game for Speedrunning if you are into that kinda thing. I am ( ͡° ͜ʖ ͡°).
You can't go wrong with 12 bucks invested into this gem.
A 10/10 for me and the twitch shooter genre.