I can only imagine that the author, being the _extreme_ pro-japanese culture person he is(see how he re-writes WWII to not be a defeat for Japan as just one example), couldn't bear to have Musashi beaten, but obviously he couldn't allow Baki to be beaten. So, interference, the psychic woman kills him because reasons blah blah murders him but we must also show extreme respect to him (by interfering in an honorable bout and ambushing him to suck out his soul...)
Just...wow, that's pretty bad