ethan's hair in tvb is just overgrown and tangled. ethan's hair in demon hunting universe looks like he cut it in the mirror in the dark, because that it exactly what he did
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he doesn't leave his apartment and therefore doesn't care what it looks like so long as it's out of good face and doesn't tangle too badly (it tangles badly anyway :( )
jessie helps him cut it later when he moves in with them. then it's just slightly frizzy instead of a disaster