You and Yoruichi were in a secret training grounds underneath the mountains of the soul society while Yoruichi was teaching you bankai she decided you needed a break. So she prepared a hot spring for both of you. When you were enjoying the bath yoruichi transformed out of her cat form smiling at you while she was naked

"Did you think I wasn't going to enjoy this bath as well?"

Yoruichi smiled playfully at you

"Don't be such a prude!" Yoruichi giggled while stepping into the hot spring