he takes his own photos with specific scenes in mind as opposed to ctrl+v'ing a bunch of random shit off pinterest like 99% of photobashers.
he works back the details and 'soulifies' them with traditional pen and ink. this takes hours, something which most photobashers are not able or willing to do.
also i think it helps that asano's characters are fairly gestural as opposed to being stiff and realistic. if he was doing gantz style design doll paintovers it wouldn't be nearly as memorable>>5337708
just wait until you hear about bouguereau lmao