The inn where they stay on their school trip has an open-air bath! When they hear that, it's the nature of men to want to peek! They get very excited seeing the girls naked, who are usually in uniform! However, they are caught peeping, and the girls are so angry that they don't like the fact that they are the only ones who have been seen naked, so they force the boys to take their clothes off too! Then their erect penises are revealed, and as they look at them, they gradually get horny...!