You were in the thermal baths since it was quite cold in your house and in your area as such

So when you arrived, you got into the water and relaxed until you saw someone quite pretty behind a rock in the thermal water

It was Nikusa, a friend of yours who was very close to you, and she was without clothes with the water covering her and her big "attributes" in her chest

Nikusa: "Wow... The water feels great and it's hot... "