Himuro Mansion had been a hot topic when I joined here in 2004, started by some person who maniacally claimed to be a Himuro descendant. The thread is in the archives, but I won't bring it up, since the delusions in the posts will make people who don't know real Japanese history to jump in and believe in the claim.
From what I know, it appears to be a game involving grisly sacrificial rites, murdering family members and others. Somewhere in the game, there is a claim that it is based on historical truth.
Himuro is just a regular Japanese name and is not an important family name in Japanese history. There is no ritual killing tradition in Japan--only killings by psychopathic or vengeful murderers, just as in any other country.
There had been incidents of whole families killed in Japan's warring period, but that was done to root out anyone carrying the blood to make sure that descendants won't take revenge. No ritualistic meaning. I'm pretty sure such family killings occurred in ancient and medieval European history as well.
Coming to Himuro Mansion, there is no such mansion. Not a single trace, both geographically and historically. I have a feeling the story was concocted by using European gothic horror stories and transplanting the satanic rituals in Japan, creating fake traditions in the plot.
So, enjoy the game if you like it, but don't be led to believe unfounded claims.
