Yeah, there's a Shiro Cosmetics Amazon store with a pages and pages of products. The listings are also properly set out, and contain more info than what is found on some of the Shiro webstore pages.

For instance, this Amazon balm contains fuller info than the webstore, which would make me think it is run by Shiro, especially since some of that extra info names Lauren, too. So does the amount of products. If you were going to pretend to be someone else, you'd just list and stock their most popular products, because sod spending all that time trying to dupe 11 pages of products, labels and colours. The store is also years old, with the seller answering questions about ingredients and formulations.

TLDR; I'd be really, really, really surprised if that Amazon store was not theirs. :P