Marriage registration / spousal visa question

Hi. I’ve got a specific visa question that I was hoping someone could help with.

I’m a British national marrying a Japanese national. We plan to register our marriage here in Japan and continue to live here.

At some point next year I’m considering applying for a spousal visa. Looking at the form in preparation it suggests that I need proof of having registered our marriage both in Japan and in my home country.

As far as I have been able to understand it, the UK will not let you register your marriage if you have already correctly registered it in a different country.

I have found a form for an overseas marriage certificate on gov.uk. And I was wondering if that’s something I needed?

Have other UK nationals (or anyone from other countries where you don’t need to register your marriage if you’ve already done so abroad) submitted successful spousal visa applications without any documents from your home country included?

Have I misunderstood the process in any way with regards to just needing to register my marriage in Japan and not the UK as well?

We are hoping to visit my family over Christmas to celebrate with them and I don’t want to miss an opportunity to register our marriage or source some sort of paperwork while we are in the UK, especially since it might be a while before we both get the opportunity to go over together again.

by soyabean24