Yukari is a temptress. Were you to live in the Yakumo household, either because of Chen or Ran, Yukari would still be there to tempt you. I have put much thought into this, because Ran is my favorite touhou and I do not have room in my heart for another.
But Yukari gets what Yukari wants. She must emanate an entrancing aura as she walks, a lustful heat that brings about the carnal desires of any man in the vicinity. She does not even need to lift a finger, as over time man's reason will crumble without any intervention, and it is then, when he is most vulnerable, that she shall strike.
Her very existence is like a perpetuating lewdness that surrounds and engulfs everything. This woman is not to be trifled with, /jp/. She is more than capable of making herself seem cute and innocent, but before you know it you will belong to her. Your entire being will be consumed as she regularly squeezes every drop of semen from your bloated penis.
You have been warned.