Madame M
It depends on the rules of your world. If One God is the only God, and is providing the power of the holy water, AND, if the Japanese demons are simply branch offices/entities of Hell, Inc., then perhaps it could. But If Christian magic only works on Christian beings then no, it wouldn't. Japanese demons seem to be more mutants with super-strength rather than Christian-hell-inspired demons.
The Toshokan Kid
No. Actually, when Christianity was banned in Japan, some Christians were rounded up and drowned in holy Japanese water.
?
Neither demons nor holy water are real.
?
No Japanese demons fear noise more chimes to firecrackers. you also need a demon wall behind your door as they like to travel in a strait line. That keeps them from entering the home.
G C
Neither demons nor holy water are in the world today.