That's the joke - there is no such key as b-sharp minor or major.
I sat down at the piano and discovered this myself, but then thought maybe I was missing something. Just give me the ‘stupid-question-of-the-day’ award.
O no, I am the stupid dumb-ass here - I wrote also b-sharp minor/major for that b-flat minor/major pair in my homepage
Ok, I meant that b-flat minor prelude and fugue. It has 5 flats - for every voice one flat
Just counted - if I am right, b-sharp minor would have 9 sharps, b-sharp major would have 12 sharps or so.
The only excuse I have is that in German the naming is total different:
B <-> H
B flat <-> B
D flat <-> Des
C sharp <-> Cis
The advantage of the German naming is that only a German can handle the famous key sequence in a proper way (numerous pieces for that notes were written including from old Bach itself):
Interesting maybe, for that c sharp major pair with 7 sharps there seems to be another score, coded with d flat major and 5 flats. That's something every Chopin lover will appreciate, since it is one of Chopin's most used keys, so one is more used to that. If anyone has the fugue coded as d flat major instead c sharp major I really would be interested to get a hint for a source to buy that.