Wash off the mud and dirt

Hermione knew that she was filthy after her trip to the greenhouse. She made her way, doing her best to not leave behind any dirt, to the prefect's bathroom again.

Before she got into the tub proper, she secured her wand inside her bag and went into a shower. She turned on the warm water, which made the showerhead squeal, and stepped under the water. Already the mud was starting to drip down the drain.

As she started to scrub the dirt that still clung to her body as best as she could, Hermione saw that the portrait of the mermaid was awake and peeking at Hermione's arse. She evidently wanted to make up for yesterday, when she missed the show with Hermione and Daphne.

Hermione, enjoying being watched, decided to give the portrait a little show, arching her back to brandish her small breasts towards the portrait as she wiped the dirt from her arms and bending over to get the dirt off her feet and legs. The mermaid was getting more and more excited, as she was now massaging her own chest.

Hermione grabbed a shower stool to sit on. She spread her legs wide open as she cleaned off the bottom of her feet, taking care of any remaining dirt there. The mermaid moved her hands to her tail and parted two fins where the groin would be on human legs to reveal a tight hole.

Now that Hermione was sufficiently clean, she made her way to the taps at the bath, purposefully trying to make her hips move as much as possible. She may have had some reservations about putting on this kind of show around anyone else in the castle, but she knew the mermaid was safe. After all, in her years at Hogwarts as a prefect, she had never seen the mermaid leave the portrait, nor have any guests.

As Hermione turned on the taps, she laid back in the enormous tub, displaying herself in her entirety to the portrait, who had begun to play her hole.

As water filled the bath, Hermione floated on her back and moved one hand to her breast to pinch her nipple while the other moved down between her legs.

The two played with each other, even as the tub filled up all the way before turning the taps off by itself. As the mermaid began to put her fingers inside herself, Hermione did the same. If the portrait could speak, it surely would have moaned as Hermione did.

In only a few minutes, they both came. Hermione floated there as her juices mixed with the waters of the bath. She looked up to see that the Mermaid's juices had coated the rock she was perched on.

"Sorry about that..." Hermione said. "I don't know how to clean that up for you..."

After she had recovered, Hermione got up and dried herself before putting on one of the three borrowed robes she had left and figuring out what to do for the rest of the day...