Fun fact: long before time had a name, Sousuke used to be a Demon Slayer OC, then he changed to a HSDxD OC, then he was both, then I scrapped the entire idea and made him completely original.
I can't really make crisp drawings in that style because I don't have the means to draw digitally and most of my markers are dead, so I'm stuck with solely pencil. Although I do enjoy the gritty look of my drawings, so I suppose it works out for me in the end.
I usually make a rough draft of all my OCs on paper and mainly just focus on the overall concept rather than detail (Hence why Chiharu's face doesn't really look like the Demon Slayer art style) but once I got the concept down, I go in and make a final version digitally, usually making some design tweaks and other things while mainly focusing on really making the character look like the art style from the media they were inspired from.