Quick update in case it helps anyone. I dropped by the shop today to pay the fee and secure my appointment. I had very low confidence in my ability to explain that I was paying for a future appointment, so I just had a message typed into Google translate that I showed them. I was a little thrown off by the 8-10 men in the lobby and thought they were customers, but they all immediately welcomed me, so they were actually staff. One younger guy did speak a bit of English and that plus my shitty Japanese/phone made everything go smoothly. Yoshiwara was very quiet at noon on a Saturday, but judging by the number of shoes in the Segretario lobby they were actually quite busy...