Sorry in advance if this is not the right place, I checked through the About tab and didn't see anything specifically against this but also realize this isn't exactly the type of narrow specific question that seems to be the purpose of this sub.
I'm specifically looking for historical information about Hokkaido during the Muromachi and Sengoku periods and what I've found on Youtube / Google so far I'm only finding broad level information about Japan as a whole during the periods. I'm probably not using the best search queries so my apologies in that regard. I've found a little bit of what I'm looking for on Wikipedia but want to build a better perspective of the time period than the few paragraphs there afford.
Does anyone have suggestions on any books or authors that I might look into?
The history of now Hokkaido from the 14th to the 16th century was essentially a history of the Ainu people in their own culture's formative period, and their interaction not only with the mainland Japanese (called Wajin), but also other groups of people around the Okhotsk sea region. Of course, the expansion of the mainland Japanese into Hokkaido (then called Ezochi) from the south and the conflict between the Ainu and the mainland Japanese was a part of this history.
I suppose some good introductions for non-academic purpose are to be found in the English language section of some historical as well as Ainu historical-cultural museums in Hokkaido itself, though the English site of the new Ainu museum (Upopoy) is a bit disappointing in regard with the lack of actual information online:
If you are interested in Ainu people's interaction with the Mongols in lower Amur River, I'd also strongly recommend to check /u/_dk's comment in how much of the modern russian far east did the chinese explore?. The comment also cited some Anglo-phone books on the topic, though I suppose they are primarily for the specialists.