It's good these shocked parents don't live in Japan.
Amazon Japan sells hardcore adult DVDs, sold by and shipped directly from Amazon and even eligible for Prime. The only age verification for the "adult" category under DVDs is users have to click the link that says "Yes I'm 18 years or older."
(Non-affiliate link for your reference)
https://www.amazon.co.jp/%E3%82%A2%E...&redirect=true