Participants who have been diagnosed as reflux esophagitis based on Los Angeles (LA) Classification Grades A to D, undergoing maintenance treatment with PPI other than vonoprazan after initial treatment, and with Pittsburgh Sleep Quality Index (PSQI) global score >= 6.0 at enrolment (VISIT 1) will be eligible for study entry and will be administered vonoprazan 20 mg once daily for 8 weeks.