There’s really not much information available in English, which is why I wrote my book, to fill that gap. There are a few books on yokai that you can find on Amazon.com, however, and you can also find a fair amount of information on Wikipedia. There are a number of legends about samurai like Minamoto no Yorimitsu fighting giant monsters; Momotaro is a famous story about a boy who fights an oni, and Kintaro is another legendary warrior character. Try doing a google search for those names and see what comes up. I hope you’ll find what you’re looking for!