http://www.aeromedical.or.jp/documents/ManualforAME.pdf
That link is to the JCAB medical requirements, translated in English. Ch1.
Medical Standards
The systolic pressure must be lower than 160 mmHg and the diastolic pressure must
be lower than 95 mmHg. Furthermore, the applicant must not have orthostatic
hypotension accompanied by subjective symptoms.eck page 27.
4-3 If an applicant's blood pressure is controlled within the standards by taking antihypertensive drugs listed below and no side effect occurs one month after
continuous dosage, he/she is qualified.
(1) Diuretics
(2) Calcium antagonists
(3) Beta-blocker
(4) ACE inhibitors
(5) AⅡ receptor blocker
While these are the JCAB requirements, your initial medical by the company may be more restrictive.