Here are the main Black Friday Deals on Amazon.co.jp. They end on December 1st.
* 50% points back on all manga published by Shueisha including all Shonen Jump manga
* 50% points back on all manga published by Square Enix, including The Apothecary Diaries.
* Bundle sale: Buy 4~7 titles get 5%, Buy 8-11 titles get 10%, Buy 12-15 titles get 15% points back (you need to activate this campaign first before buying)
For more details, please go to https://www.amazon.co.jp/-/en/hko/deals/
Detailed instructions on how to buy kindle books from aboard: https://www.tofugu.com/japanese/how-to-buy-japanese-ebooks/