The main type of weapon used by Kaiman, Aikawa and The Cross-Eyes, coming in a wide variety of forms, they are simple Knives, with no magic properties, yet their users are always extremely skilled in melee combat, making them terrifying weapons during a fight.
Kaiman has a collection of them in his home, as shown in Chapter 3, all of them reminiscent of M-16 Bayonet Knives. He tends to carry at least 3 on him; consisting of one M9 Bayonet and two M7 Bayonets.
Aikawa used the same type to chop the arms of his old teacher, leaving him fainted in pain. In future chapters we see he still carried them, using one to try to kill himself, in hopes to also kill the sinister entity inside him.
Ton uses trowing knives, sporting an extremely accurate aim as shown in Chapter 52.
Dokuga uses the same set of Bayonet Knives as Kaiman and Aikawa, but also, for a brief moment, The Boss Combat Knives, custom made machete-like blades with shotgun handles. They where entrusted to him by Kai himself before his disappearance, and Dokuga returned them to his rightful owner once he came back.