Yuusha no Party ni Eiyoushi ga Kuwawatta!  

勇者のパーティーに栄養士が加わった!

Kavin, the main character in your story, has been tasked with rescuing the princess from an untreatable ailment. However, his own digestive issues are hindering him and his companions' progress. Following a severe bout of diarrhea, he encounters Hanae at a restaurant who specializes in nutritional advice. She assists Kavin in consuming a meal that won't cause further discomfort to his stomach. Inspired by this encounter, Kavin decides to include Harue in their group to ensure everyone is eating healthily.