They are indeed strawberries. Japan has a culture of breeding and selling crazy looking & super delicious fruit like white strawberries that are supposed to be super sweet or cube shaped melons or grapes the size of quail eggs, shining and about to just explode with juicyness and flavor when you put them in your mouth. You can dig into this topic via google, I just did it at year ago when I found out. The prices for these fruits are insane hence we don’t see them in normal supermarkets or even barely outside of Japan. In Japan people give each other pieces of these fruits as gifts and symbols of gratitude, like think of the student who will give their professor white strawberries after completing studies and finishing a year with a good grade. Of course, there are global trade businesses that export this stuff out of Japan and sell it mainly to yacht owners because that’s where money doesn’t matter anyways.