SW-1030 Mixed bathing with my grown-up nieces on a hot spring trip! A naughty girl secretly grabs my erect dick. I'll secretly fuck her when no one's around!

I went on a hot spring trip with my nieces, whom I hadn't seen in a while. They found me peeking at them while they were changing and invited me to take a bath with them. As we washed each other for the first time in a while, they noticed that my penis was erect and started stroking it while pretending to wash it. My niece is grown up and in heat now, so it's okay for us to have sex alone in the bathroom.