Back Door at Milk Massage (aka MM)
[QUOTE=WayneAshley380;5898921]Yes.
If you don't back in there's a door in front of your car, to the left.
I've been taken out that way but never went in.
Others have said that all you have to do is knock.[/QUOTE]This "back door" is actually a SIDE door very near the back of the building and is, as WayneAshley describes, right next to the parking lot. This back/side door is also very visible in most all GOOGLE MAPS STREET VIEW images... so do THAT if you'd like to see this visually.
The ENTRY access comes with a lot of variability because Keiko's "office" is at the FRONT of the building and if you knock on that door and STAND THERE, it could take up to a few minutes for Keiko to finish whatever duty she's occupied with at the front (if any), notice you on the exterior security camera, and then walk ALL THE WAY down that very long hall to get to the back door to let you in. She may call out to the cleaning lady on duty to let you in, or, if you're REALLY lucky, that cleaning lady is already near the back taking care of laundry (or whatever) and can hear the knock on the door. Either way, they're not going to just open it up because they hear a knock on the door. The FIRST thing they'll do is look at the security monitor to check out who's standing there (and assure it's not a SWAT team with a battering ram, or something equally nefarious).
So, the short answer is YES, you can try to get in that back/side door, as long as you don't mind looking MORE conspicuous standing there (for what could be several minutes) than you would simply briskly walking in the front door of a business storefront on an extremely busy roadway where NO ONE is paying any attention to who's going in and out of that front door.
Personally, I always try to park near that back/side door, then I simply walk in the front and when I LEAVE, as WayneAshley has done, I EXIT through the back door (at my request) so I don't have to pass anyone coming IN the front. I'm surprised Keiko hasn't formally set up the traffic flow to force this entry/exit pattern, but it must not be a problem for her to just manage the front so as not to "release" anyone through the front door if there's an incoming customer at the same moment.