Aside from being female, and awesome, Shigure hasn't gotten the chances to train with Kenichi that much, so I hope she doesn't die.
I can see how this goes down:
Eclair be like: "A promise to an old friend is worth more than money (still secretly taking the gold bar afterwards lol)" and protects them all until the 4 masters arrive for the showdown.
Kenichi's growth: He be like: "If I stay still and run, I won't ever hope to become a master (and marry Miu)." So he be all suicidal and luckily lands a few blows on them masters, buying time for the 4 masters to come.
Both of those options happen
Both of those options, with the addition of Miu and Microft backing them up.
Shigure uses some badass moves to buy time until the 4 masters arrive.
Badass Invincible Superman arrives otu of nowhere, carrying with him the beaten-ass legendary master of the weapons' division.
Least and worst possible option: Shigure dies. (Fuck this option)