I finally found the source of the Nagasakiya Mario Tennis cards… and its wonderfully called “Virtual Boy Candy”. This candy expired in September 1996! Its an incredible box that explains that there are indeed 10 cards to collect, and two stickers (each box had 1 random card/sticker). Based on the ingredients list, I suspect this is some kind of hard candy. I do not have the heart to open this box as it requires tearing the top or bottom. I wonder if the candy is a VB shape, or red in color, or if there is a paper inside showing what all 10 cards are, and to mark them as you collect them. Who knows. We will have to just keep the contents a mystery.
Scans of all sides of the box will be uploaded to the archive shortly. Until then, here is an attached photo of what I consider the complete collection. The 10 loose cards, 2 sealed examples with the 2 types of stickers, and the sealed box with candy.