A mother and son went on a trip to a hot spring. It had been a while since they had been to a hot spring by themselves, and they decided to take a bath together. They went into the open-air bath together. It had been a while since they had seen the mother's ripe body and the son's strong body. They were excited by each other's bodies, and even though they knew it was wrong, they couldn't help but seek each other's bodies in the open-air bath.