Sadly, there are merely a handful of websites that have anything whatsoever to say about Hundred World Story...
100 Worlds Story: Tales On A Watery Wilderness FAQ/Walkthrough
by Raging_DemonTEN. I think this used to be on GameFaq, and there were complaints that it needed work. Also, some of the info is wrong, and it doesn't seem to be aware of all of the possible endings and monsters. Still, it's by far the best this game has got.
Gameman's two-page review on +D Games has more to say about 100 World Story than any other review I found, but sadly for me it's in Japanese. The Google English translation is entertaining though.
Video Game Endings: 100 World Story
A few entertaining endings, but note that there are many more possible endings than those shown. Look out for ridiculous pop-behind ads.