I've said it many times before, the buying the book DOES NOT support the author, it supports the publishing company. The author sees NONE of that money. Instead, find their patreon, and donate that way.
@princeofcups Well. what if there are none? I'm checking this author and some other authors pixiv and social media such as twitter, and I didn't find their patreon.
Oh but I do find patreon of "Merryweather", (not to sound like I'm dissing) but this person only does webcomics though, Merryweather don't have books to sell (as far as I see it).