Dude, I love your Anime / Manga drawing style / skill! The Sig is OK, done well and looks professional. No need to improve. I just don't get the meaning of your Sig. That guy is some kind of an emo-suicidal, who wants to kill himself, because his time is running out? I would give him a Hero attitude and aim his weapon double handed against the viewer in a suspended perspective. With that the message would turn into: "Dude, give me what I want...YOUR time is running out!"