The site crapped itself and I couldn't see what I was typing. At any rate, what I was trying to say was, even without having read any of the other series (which is amazing to me), it was already explained what he was burning, several chapters ago: https://mangadex.org/chapter/ec3337fc-2b38-43f9-9c7b-58403153837a/5
It's his wankrag, no, I mean it's the symbol of Ryushin's motorcycle gang The Front of Armament when he was a younger man. This all originates from Crows, which is the series where Suzuran, Zetton himself, and other notables first made their debut in.
The site crapped itself and I couldn't see what I was typing. At any rate, what I was trying to say was, even without having read any of the other series (which is amazing to me), it was already explained what he was burning, several chapters ago: https://mangadex.org/chapter/ec3337fc-2b38-43f9-9c7b-58403153837a/5