I've been to certain shops with a friend of mine who is Japanese/Caucasian mixed, but very obviously mixed, who also holds a Japanese passport, spent the majority of is life in Japan and is absolutely fluent in Japanese. The second we walk up to the door, doorman looks at him and gives him the crossed arms. He tells the guy off in fluent Japanese and still, arms are crossed. Doorman looks at me, gets confused and starts lowering his arms until I blurt out, "FUCK THIS PLACE, MAN!" and then the arms come up again and he starts shouting for us to leave.
If that's what they do to half WHITE guys, I can only imagine what they'd do to half black...particularly since "half black" in Japan, for all intents and purposes, is the same as full black.
Next time you get cockblocked by some racist tencho, whip out that 9.5 inch monster you were describing earlier and wave it at him. You aren't getting in, but at least you'll get the satisfaction of watching the color drain from his face as his dick and self esteem shrink and wither and he goes home traumatized with an even more ferociously burning hatred of black folks. I say, if they're gonna hate you anyway, may as well give them a good reason.