I'm curious about page 6, do those kana actually typically correspond to those alphabet letters for Japanese keyboards?
As an aside, that keyboard design reminds me so much of Logitech's wireless MK270: https://pisces.bbystatic.com/image2/BestBuy_US/images/products/1440/1440638_sd.jpg
She should have put all the key caps in a plastic bucket, bowl, sink, or equivalent with water and detergent. Then she could have cleaned them in bulk with a brush, not one by one.