noun
mystery shopper; secret shopper
A person hired to pose as a customer and evaluate service quality, typically in retail or hospitality.
彼女はミステリーショッパーとしてレストランのサービスを評価した。
She evaluated the restaurant's service as a mystery shopper.
Variant with interpunct; less common in running text but seen in titles or emphasis.
Borrowed from English 'mystery shopper'.