Yoki, being a courier/messenger, thinks that legs is most important thing in her job, so she spend most of her training days working with legs. You can say, she never skips leg day x)
And she trying so hard so most of her people still surprised how much she managed to develop her legs, and she considered as fast as many-tailed kitsunes. But besides this, she has all common features for one-tailed kitsune.
Some of kitsunes tried reach Yoki's level, but soon or later they're found such training process too monotonous and unpromising. But for Yoki, it's somekind of ideafix, childish ideal she wants to reach - being fastest one-tailed kitsune, with mountain-crushing power.

Yoki - Me

Art - RadarRid3r (https://x.com/RadarRid3r)