Well, the results of applying the huge enamdict Japanese name dictionary are of questionable utility.

Even after excluding all the detectably foreign names (any that are written with katakana at all) along with placenames, products etc., it turns out that there is a relatively large number of rare Japanese names which actually collide with western names -- examples are:

Surnames:
DEE      (出江)
DOUGAN   (道願)
HANNA    (伴奈)
HANSEN   (飯泉)
HENRI    (片理)

Forenames:
ANNE     (晏音)
BEN      (勉)
MINA     (茉奈)

and more. The result is that the number of Japanese Provisional climbs from the zero I'd got it down to back up to 107.

I'm going to think about this over the weekend and decide whether the perceived improvement in trustworthy evidence going into the process justifies the extra work to disentangle these new candidate Japanese names (very few of which, I think, are actually Japanese).