The gas hidden in the abdomen wants to get out. School girls in the middle of youth want to do it when there are no people if possible. But Gus walks its steps from her intestines to her anus and touches the curtains on her sphincter! The second wave, the third wave and so on come out one after another without worrying about such a thing. Somehow people vented the gas when they were away, but they came back soon and got caught, or they came out at a quiet moment in class and echoed in the classroom. The girls who became embarrassed escaped to the bathroom and slammed there as well.