It already starts with the name of the game. "Dragon" does evoke a very different image for people in Asia than for us. Or take the Devils/Demons. Baator and Celestia in D&D are inspired by Dantes Divine Comedy and while most players here have not read it, this book has shaped our culture and our understanding of Heaven and Hell is still based a bit on it. People in Asia will have a very different concept of those things as well.
Japanese popular culture (manga, anime, video games) has been full of explicitly Western fantasy elements for a very long time now. Western-style knights, demons, and dragons are staples there. It's not all
ronin and
oni. Far from it.
Take any Dragon Quest game, or any number of anime as examples. You could start with a current one, Rage of Bahamut: Genesis (based, apparently, on a popular collectible card game). One of the main characters is "Jeanne d'Arc", leader of the "Orleans Knights". The bad guys include "Lucifer" & "Azazel". There are angels, and faux-European cities. Heck, one of the protagonists is named after Sergio Leone -- complete with appropriate musical cues.
Sure, Japanese media make a crazy hash out of these Western elements, but no more so than your average D&D campaign.
Unfamiliarity, or a lack of resonance, can't explain pen-and-paper RPGs unpopularity in Japan (and it's specifically PnP RPGS... CRPGs featuring Western fantasy stuff are, again staples).