Study to Evaluate the Efficacy and Safety of Combined Administration of TAK-536CCB and Hydrochlorothiazide in Patients With Grade I or II Essential Hypertension.

Inclusion Criteria: 1. Grade I or II essential hypertension. 2. An office sitting systolic blood pressure of ≥ 150 and \< 180 mmHg, and an office sitting diastolic blood pressure of ≥ 95 and \< 110 mmHg during the placebo run-in period at Week -2 and Week 0. 3. Male or female aged 20 years or older at the time of providing informed consent. 4. Outpatient. Exclusion Criteria: 1. Secondary hypertension, grade III hypertension or malignant hypertension. 2. An office sitting systolic blood pressure of ≥160 mmHg or sitting diastolic blood pressure of ≥100 mmHg recorded while on combined therapy with 3 or more antihypertensives within 4 weeks prior to the initiation of the placebo run-in period and at Week -4. 3 Evident white coat hypertension or white coat phenomenon. 4. Day-night reversed lifestyle, such as night-time workers. 5. Sleep apnea syndrome requiring treatment. 6. Have any of the cardiovascular disease or symptoms listed below: * Heart disease: myocardial infarction (within 24 weeks before the placebo run-in period), coronary arterial revascularization (within 24 weeks before the placebo run-in period), severe valvular disease, atrial fibrillation, or following diseases which require medication: angina pectoris, congested heart failure, or arrhythmia. * Cerebrovascular disease: cerebral infarction, cerebral hemorrhage (within 24 weeks before the placebo run-in period), or transient ischemic attack (within 24 weeks before the placebo run-in period). * Vascular diseases: peripheral arterial disease with intermittent claudication, artery dissection, aneurysm * Advanced hypertensive retinopathy: bleeding, exudation, or papilledema (within 24 weeks before the placebo run-in period). 7\. Clinically significant hepatic disorder. 8. Clinically significant renal impairment. 9. Significantly low or high Potassium or Sodium levels. 10. Complicated by gout, or had a past history of gout within 24 weeks prior to the initiation of the placebo run-in period, or complicated by hyperuricemia requiring medication. 11\. Diabetic subject on insulin treatment or poorly controlled type 2 diabetes mellitus. 12\. Have a malignant tumor.