Red Blood Cells are summoned to handle an emergency. They carry as much oxygen as they can to the scene, but they discover that the stomach has an ulcer and is badly breached. If the serosa becomes perforated, the stomach will end up melting down. Due to the excessive secretion of gastric acid, the body may die at any moment, but the Red Blood Cells continue to desperately carry oxygen. However, the gastric mucosa is being eaten away, and inflammation is getting worse. In such a disastrous situation, a dangerous enemy appears.