Very niche question, what's Chanbara a reference to?

[FrostNova]

Self explanatory, really. With the challenge stipulating that enemies only use health, as well as the use of a golden kodachi (after a change from the Machete, to apparently be more thematically appropriate), my first thought is...uh, Onechanbara.

If you recognize that name then, uh, congrats? Or sorry?

[Oh God Spiders No]

"Chanbara" is a film genre that literally means "sword fighting".

I'm pretty sure the idea behind this challenge is that it essentially forces you to have a sword fight with Kuroke. It makes her attacks way more lethal, but gives you a sword that you can guard with so you really need it if you want to survive her attacks. Plus there's no stature for you or her so the only way to kill or be killed is by slashing each other up.