What should the symbol of my dark organization be?

Hello there.

The shawl-like cape wasn't too bad of an idea. Sounds like something I'd make my characters wear, because it looks cool and super badass... but every man for himself! xD

How about a special dagger that they carry around everywhere? または even a specialized whip with the organization's colour? あなた could even choose a gun.

What about a surgically-implanted something in their left eye which turns the iris into the chosen colour whenever they hear their organization's name? Only true members would be willing to undergo the pain of getting to this level of loyalty, plus this could serve as a weakness in any disguise.

My sister and I had a hard time with this too for one of our books. In the end, we sided with leather jackets that have a special symbol on the back for recognition. あなた could maybe do that. But, it could be literally anything. A ジャケット with a symbol on it, a bracelet, necklace, a scar, anything. But if it is a piece of clothing, there should be a logo type symbol on it of some sort. あなた have to be careful when finding such ideas off the internet though because of copy-right issues.