As C.B. stated it has been said before.
It's Soongsil University station (Line 7)
Exit 2->walk straight 200 meters down the hill slightly->pass By The Way-> look for the Stress Clinic sign
C.B it sounds like it was too bad for you. I have had the one you mentioned I think, but last time I got lucky and had a gorgeous one. Did you play with the titties? Don't wait for the invite, and just ask for the mileage cards.
In other news, my friend went to Yongsan and tried a back alley "babe". They weren't bad to tell the truth. I almost considered pounding one cutie, but it was kinda morning by then and I figured I'd enjoy it more another time. My friend took about 25 minutes and said that there was no rush and a huge set of mama titties on her. Too bad its fuck but no suck.