It really is a Kumeleon gun, gunblades are inherently cool.
The executioner design is really cool too, I don't frequently see designs that implement such details as having two arms on the same side to use a compound weapon like that, and the shield opening like a mouth to absorb energy was an really fun detail, instead of simply absorbing the energy, it "ate" it.
Another fun thing is how the design of the swords leads you to see that there may be a trick to it.
I looked at the cover page and found the design of the "crossguard" a little off from the rest of the weapon, but thought at first it was just a design choice by the author, and in the end... my instinct was right I just wasn't able to decipher why, really smart use of visual storytelling.
The fights in this manga are really good, they are few in between but when they hit... they H I T.