a customer who visits 《the restaurant》 for the first time, with no introduction from 《its》 regular customer
a chance customer.
外観だけから
(from appearances alone)
読み方 いっけん
A look; a sight; a glance; a glimpse:(=する) to take a look at, have a look at (anything); to cast a glance at (anything); to catch a glimpse of (anything)