The cerulean is a huge 5 star hotel in Shibuya wiht a large lobby with a lot of traffic. I can't imagine any problem bringing in your date in, a long as sh eis not dressed too obviousy like a ...
I recall having met the legendary Manami, while she was still with Am at the Imperial. She had no problem going in and up to my room. She had just put on a large coat ( it was winter) around her shoulders, masking her sexy outfit...