To the left of the saddle horn, like all the other dangly bits.
Hey, if it's just a friction rash, it will probably respond to hydrocortisone cream twice a day. Wash and dry the uh, area before applying. This can sometimes work within a day and a half. If there is some kind of fungial action going on, it's a whole 'nuther story. I don't know your sources in China, but in the US, you can pick up a tube at any drugstore.
I doubt cycling shorts contribute to the problem, but you must have a reason for your opinion.
Some people are like a Slinky ... not really good for anything, but you still can't help but smile when you shove them down the stairs.