Dude whats this?! all this time Miyoko managed to defeat Saki over and over right? how come she is losing against that other chick? in fact she is not defending at all!
She wasn't defeating Saki over and over because she's stronger than Saki. She defeated Saki because Saki's heart was never in the fight. Hell, Miyoko's probably wasn't either, so I doubt either of them is really used to fighting somebody that's really serious. They've basically been play-fighting this whole manga, although Saki, at least, doesn't seem conscious of it.