She relieves herself in more ways than one

All too soon, the trickle of piss slows and stops, her bladder empty. Already, Hermione misses the feeling of squeezing liquid through her sensitive urethra. She sulks for a moment on the toilet, gradually deciding to continue her enjoyment. Her fingers dip between her thighs, and she hooks them around her pelvis, searching for the familiar adjacent hole. She finds it, and pushes her fingers up into her vagina with a quiet gasp.

She fingers herself on the toilet, muffling her soft moans with the other hand. A few squeaks make it out of her as she finds her stride, and soon the muffled wet shlicking sound joins her involuntary muted yelps. She masturbates quietly on the toilet, hoping that there’s nobody to hear her self-pleasuring.