I've already married three Japanese people: I expect there will be more.
I'd better put this up front: I only have one wife. And I've only ever had one. We're very happily married.
But a few years ago a Japanese friend of mine asked me to officiate at his wedding. He wasn't a Christian, and neither was his fiancée (now wife) but he and I had been regularly reading and discussing about the Bible together over a period of some months, and he wanted to make his vows before God. As I understand marriage to be an institution of God's "common grace," I was glad to marry them in the sight of God. That's why I say I've married three Japanese people.
Since the 1990s, the majority of Japanese weddings have been "Christian" ceremonies. Wedding "chapels" (which often look like stereotypical western church buildings) proliferate throughout Japan, and represent big business. Just round the corner from our apartment, there's a "church" (yes -- that's what it calls itself) which is really a business catering to couples who want a western-style wedding ceremony, with all the trimmings. This one is designed to look like a street scene in Italy. I took a photo of it last night.
Most of these "Christian" weddings have nothing to do with Jesus Christ, except perhaps in name. The "pastor" who officiates needn't be ordained: in most cases he (and it's always he, at least as far as I have ever seen) needn't even have a real Christian faith. If he looks foreign and can mumble his way through a bit of Japanese "liturgy," he can get quite well paid for his service. Christians can, and I think should, look on all this with some real sadness -- what a confusion and corruption of real Christianity!
And yet there is perhaps something positive that Christians can take from the wedding chapel industry: the Japanese view of Christianity, in general, is not bad. It's not that Japanese people are queuing up to become Christians, or to study the Bible, but many of them are not hostile towards Christianity. In some ways, there is less outward hostility to the gospel than there is in Europe. Surveys in recent years have indicated that up to 10% of Japanese say that if they had to identify with any particular religion, they would choose Christianity.
Many of those who come to faith in Christ after childhood had some exposure to "Christian" things as kids, whether that was in a nominally-Christian kindergarten, or even a "mission" school (which may or may not have had much real Christian influence). These experiences can clear away some of the suspicion that might otherwise attend Christians and churches in Japan. It's at least possible that wedding chapels have a similar effect, for some at least.
I'm not about to begin a wedding chapel "ministry." But with the opportunities there are and interest that there is, I'd be surprised if I never marry another Japanese person again. I just need to make sure to clarify what I mean by that... to my wife!