I went through this shit last night, but I guess I'll bother typing it all out again just for you, you're a lucky man.
Shinkurou wasn't confident with his Hyozuki (sp?) fighting style enough to use it before, but he tested it out once. Remember the part in one of the earlier fights against Lin when he said, 'wow, I hit her!' he was trying the Hyozuki style I assume. Benika's style is what Shinkurou was fighting with before, and they all knew it well so it was easy to predict. Not only that but Benika's style was strict and systematic. The Hyozuki style 'has no stance' and is hard to predict, so Ryuuji and Lin could no longer defend against Shinkurou and Lin once they decided to use it. Benika was still getting her ass kicked if you noticed, it was the use of this new fighting style that gave them the upper edge. The only reason Lin was able to beat Yayoi before is because she knew her style, as soon as Yayoi tried something Lin hadn't seen before Lin didn't stand a chance.