you may need to change your given name too
I took my wife's family name when I got married.
With all the press about the illegality of keeping ones maiden name after marriage in Japan ("bessei kekkon"), and being opposed to "bessei kekkon" myself, I thougth that I would be able to change my name to my wife's name using the Japanese system upon marriage.
However, since I am not Japanese and do not have a "koseki" (domicillary register) I can not merge our "kosekis" to be registered on the koseki of my wife. I instead a footnote. It says on my wife's koseki that she has married a gaijin.
Unperturbed, I changed my name under British law (which is as easy as writing a letter to yourself called a deed poll of change of name, and then getting ones passport/bank etc changed).
Once my passport was changed, I was then called by my wifes name in Japan but NOT with Japanese characters since it was changed and registered under the British system. If I wanted to have the Kanji officially, I would need to become a Japanese national.
I am allowed to put my wife's name in Japanese characters as my handle/nickname "tsuusho" on the back of my gaijin card, and for the most part my employer and others agree to write my family name using Kanji.
HOWEVER,
and here is the big minus, I find that now that I have a Japanese family name and an English given name, a great many Japanese choose to call me by my given name even in formal contexts.
I usually write my name in Japanese word order in Kanji followed by English letters. Sort of like this 田中Larry. When I had an English name I used to write my name in the same Japanese order and people had no problem calling me by my family name. Now however, the majority of Japanese people call me "Larry-san." Some claim that they think that my surname must be the Larry. It seems to me, however, for the most part it just grates with them calling me by a Japanese name when I am clearly not of Japanese descent.
No one else at my place of work is called by their first name. My workmates are unable to pronounce my Englsih first name. My Japanese surname is a common one. And yet, I am still called the equivalent of "Larry-san."
Recently there was a drive to be fair to women and not "chan-zuke" (call them ~chan) them. I asked our equal opportunities board to add to this campaign the drive to avoid calling non-Japanese by their first names (unless they specifically asked to be so called) but so far my request has been met with misapprehension: "It is true that some gaijin may prefer to be called by their surname but others may not. We will discuss this further." I tried to explain that it was not a matter of preference (some women may prefer to be called ~chan) but being treated equally, but this did not wash.
Even worse the member of the anti-discrimination board whom I approached has taken to giving me a lesson in Japanese manners. Eww.
My English surname was even more difficult to pronounce than my first name. I thought that giving myself a Japanese name would make it easier for people to call me something. But so far I have not found that this strategy has been very successful. Lately, in spite of myself, I have been finding it rather upsetting.
Perhaps I will change my given name to Youhei, Takeshi or something. That will stump them
But I bet it would be years before workmates cease calling me "Larry-san," at least when I am not present.