Bookwalker Cover Grabber
Book Walker's often very large volume covers can be very useful for use in making character images or banners, or simply to have a very high quality cover you can immediately upload to the website for the XL cover feature.
- A box will pop up containing a direct link to the larger image which you can paste into a new tab to access and save. Example: https://c.bookwalker.jp/coverImage_1936781.jpg
Image Max URL, a website and userscript that redirects images to the original versions, has Bookwalker functionality included as of 0.74 - https://github.com/qsniyg/maxurl.
Please be aware that the userscript affects a large number of sites, which may not be desired.