|Sinful Shard is a backup weapon owned by Kay . It is a large knife, wielded with extreme skill and accuracy. This leaves her open for close attacks, so she rarely uses it. Even so, it's still considered dangerous within her grasp.
Sinful Shard is actually a 'Chef's Knife' or also known as a 'Cooks Knife'. A chef's knife generally has a blade eight inches (20 centimeters) in length and 1 1⁄2 inches (3.8 cm) in width. However, Kay's knife is much longer in length by being 14" inches (36 centimeter) .
It's blade is coated in some substance Kay made while messing around with it, leaving it to stay glossy and shiny, along with being unbreakable.
Kay has carved 'Sinful' into its side to remind herself and others that this knife is hers only.
While fighting a hoard of Faded, Kay ran out of bullets and needed something to hold them back. Much like how she found 'G.G,' she had been walking in the wasteland, scavenging for many things. While being attacked, she had tripped over a small wooden chest, and upon impact, the chest opened, revealing the large knife within a leather pouch and leather black belt. Kay grabbed the contents and used the knife to fight off the Faded.
Kay called it 'Sinful Shard' since she noticed a small shard of the blade was missing, and it had been stained with blood.