oh they do exist

They've been around for some time. And they are as real-life-like as technology has made dolls, ie, as real as you can find adult dolls in the USA.

As a sidenote, they have also been used to produce doll kp; now the legality of THAT is at least questionable almost everywhere I know of.

Finally, ordering from abroad exposes you to different customs than bringing it yourself. I would assume that if you yourself went to Japan and brought it back with you on the plane, customs in a passenger airport would have better things to do with their time, like finding drugs and tariff evaders, than retaining the doll... Furthermore, you would be able to bring her without her box, allowing you to disguise her as an "innocent" (wtm) toy for your niece.