The purpose of this study is to determine the efficacy of TAK-438, once daily (QD), compared to lansoprazole in patients with erosive esophagitis of Grade A to D as defined by the LA classification grading system.

Inclusion Criteria:

1. At Visit 1 (start of the observation period), the participant must have endoscopically confirmed erosive esophagitis of Grade A to D, as defined by the LA classification grading system, and the target number of participants who are clearly Grade C or D is 30% (120 participants) or more of the total participants.
2. Outpatient (including inpatient for examination)

Exclusion Criteria:

1. Participants with an esophagus-related complication (eosinophilic esophagitis, esophageal varices, scleroderma, viral or fungal infection, esophageal stenosis, etc.), a history of radiotherapy or cryotherapy of the esophagus, a caustic or physiochemical trauma (esophageal sclerotherapy, etc.). However, participants with Schatzki's ring (mucosal tissue ring around inferior esophageal sphincter) or Barrett's esophagus are allowed to be included.
2. Participants who have received surgery or treatment affecting gastroesophageal reflux (cardioplasty, dilation of esophageal stenosis [excluding Schatzki's ring], etc.), or who have a history of surgery of stomach or duodenum (excluding removal of benign polyp under endoscopy)
3. Participants who have acute upper gastrointestinal bleeding, gastric or duodenal ulcer (mucosal defect with white coating) within 30 days prior to Visit 1 (start of the observation period). However, participants with gastric or duodenal erosions are allowed to be included.
4. Participants with a previous or current history of Zollinger-Ellison syndrome, or other gastric acid hypersecretion disorders