https://mangadex.org/chapter/483024/20
I feel bad for that Guardian in that last panel there. All the other armed guardians use katana, or dao, or spear, or chain-sickle, and whatnot. All he has is a dinky knife.
I guess he's proud of his knife martial art school. Or maybe he's just proud of his mercenary nom-de-guerre , something like, "Jack the Knife" or whatever.