Character designs of siblings are very cool and inclusion of gun-fu is a cool thing. Art style also reminds me of darker than black. But small sized paneling of prolonged fights makes combat seem too fast paced to convey the gravity of hits and damage taken by both sides.
For example during the cableskull fight most of the panels are too small and attacks and actions appear too unimportant as a result.
Also square sound effect boxes are too western comic book style, while art style is 2000s manga. This makes sound effect boxes clash with scene they are in, especially due to art style having good amount of black and vfx boxes being white background.