I finally got the opportunity to test this service.
For those too bothered to read, it was ok but not great.
Details:
I chose Valentina (my first choice was mia but she wasn't available).
Making a reservation was extremely difficult. With asian mystique, it is always possible to meet the girls anywhere, and walk together to a love hotel. But here, not only did they want me to already have a room booked, it had to be in Sugamo.
The old guy on the phone wasn't really nice, although that's understandable because I had to call him numerous time to get things clear. In the end things worked out, I was able to schedule both a hotel in Sugamo (had to do it myself, people who don't speak Japanese can't do this, but I don't expect people who don't speak japanese to look for this kind of service with Western girls anyways), and the girl.
The guy had to call her to confirm if she was ok with gaijins, by the way.
When I reached the hotel, the guy called me directly at the hotel to make sure this wasn't a scam or a trap, I don't know, but this was quite a stressful experience. Also, he used the opportunity to tell me this wasn't the full thing, only "health service", and that I had to agree with the idea because lots of gaijins didn't understand that quite correctly.
This one was quite a shock. I thought it was cheap for a "full service" system, but I think it's expensive for just "health service".
The girl came to my hotel room right in time. She was the girl shown on the picture, but obviously they lied on her age, and the pictures are heavily photoshopped (or she had awesome makeup on the pictures). So, she was ok, but a bit of a disappointment. Big fake breasts, big fake but, not really my thing, but oh well. She had very cute eyes, though.
Also she is said to be English on the site, which is a white lie. She told me she was born in England, but she is Spanish, and doesn't speak English at all. All communication was in Japanese but she wasn't so good at it either. So long for the "exotic western experience"
She confirmed that it was only "health", and asked 20'000 for 1h. She then told me that "more" was possible for an extra 20'000. I guess they are allowed to do that if they like the client, or something, I don't know, but I wouldn't suggest "forcing" it on the girl unless she suggests it herself. I (really) didn't have that amount of money on me, so after negotiating we agreed on 10'000 extra for the full thing.
So the total was 30'000 for one hour (after negotiating!) which is roughly the same price as Asian mystique.
She seemed to truly enjoy her time while we were doing it, making sure several times that I was doing things she liked (which, well, I actually like the idea that the girl might be enjoying it at least a little bit...). We then talked a bit, but I wasn't in the mood for a long talk so I decided to go.
I'm not a "huge" user of these services, but after trying asian mystique and this, I'm not sure anymore if I'm just bored with the whole thing, or if was just not in the mood after all the hassle I went through to get this reservation, but basically I felt it wasn't worth the money, mostly because of the accumulation of "small issues". Difficult to book a girl, getting told it isn't the full thing AFTER I booked everything, the girl not really looking like her picture,etc...
Anyways, it was alright but I'm not sure I'll go there again soon. It is still ok if you are getting bored with asian mystique.
As Kias said, getting quality western girls is probably difficult