Opt out of NI contributions overseas

I moved from UK to Japan at the end of Feb 2024 but remain employed by my UK employer. I have received confirmation of my membership of the contributory Japanese National Health Insurance system. I have confirmed from gov.uk that I have paid 40 full years of UK NI contributions so entitlement to full UK state pension has already been attained. As such, in order to avoid double taxation, is it possible for me to opt out of UK NI contributions. I understand that income earned from the UK is subject to UK taxation and will be decalred on a UK tax return and not be subject to double taxation in Japan. My query solely relates to National Insurance.

Hi johnny Finnis,
You will need to write to HMRC to request a liability decision which will confirm if you are liable to pay National Insurance contributions in the UK whilst living in Japan, but working for a UK employer.
Please provide the following information in your letter:
•    your full name
•    your National Insurance Number
•    your date of birth
•    the date you left the UK
•    your most recent UK address
•    your address abroad
•    the type of work you do
•    your company name and address – UK and abroad 
•    where your contract is held
•    how often you work in the UK
•    your normal working pattern (the days, weeks or months you regularly work)
The address to write to is:
PT Operations North East England
International Caseworker
HM Revenue and Customs
BX9 1AN
Thank you.