Well screw you and your RNG fight too, Yuugi. You're supposed to be an oni, slow and really strong, not someone who dodges at least 1/3 of all attacks and moves twice before anyone can think.
By the way, do you get your subclass stone back if you reset someone or are you stuck with that subclass? Also kind of a silly question, but you don't need to save twelve stones to get the infinite subclass stone, do you?
There's a infinite subclass stone?

But with Yuugi, if you have either a evade tank like
or you
the battle's a lot easier. Wriggle helps a bunch, too (if I remember right, Yuugi can be poisoned, but I'm not 100% sure about this one); never underestimate poison damage.
Funny story with this battle, she killed me about 2 or 3 times, but on the third or fourth time,
decided she was The One, and only got hit with one Knockout in Three Steps, and dodged the rest as I slowly ground Yuugi down with Youmu and Nitori.
And on the subject of Subclasses, how do you get new ones? I noticed I got Tactician or Strategist or whatever it's called at some point, and I'm not sure when or where.