What exactly is "Japanese" Salt and Pepper?
They may have been trying to describe "salt and Japanese pepper". Japanese pepper is unrelated to black pepper, but closely related to Sichuan pepper; its flavor has been described as "lemony" and it has a "numbing" quality. It's also known as "sansho". Mixtures of pre-ground sansho and salt are readily available in Asian grocery stores. This mixture is commonly sprinkled on grilled meats, so this would be my guess.

Of course, it's also possible they meant black and/or white pepper. There's a number of varietals of peppercorn, and how they are roasted, stored, and ground will have a significant effect on the taste.