Do people feel awkward or funny calling you by your new Japanese name? Or do they use nicknames?
This does not, at least in my opinion, change with naturalization, although at least the confusion is a little different than it was before. I'd also like to hear what our male bloggers have to say about this one... because as a woman with a wedding ring I possibly get a slightly different treatment in certain respects.
I can think of exactly one time when someone has given me a hard time about my last name. Most Japanese and foreign residents of Japan seem to have no problem accepting me as "Ito-san." I do believe, however, that even people who do not know me or my husband are probably assuming that I'm married to a Japanese man. The one time I was literally harassed because of my name happened in my waitressing days, when a group of middle-aged men decided to use our restaurant as an 居酒屋 (Japanese pub) in the middle of the afternoon. After a few drinks, they started saying things like "That's not your real name, is it? What's your real name? Why are you pretending to be Japanese?" I just said "It is my real name. Excuse me," as politely as I could and left, but it did make me wonder if other people aren't thinking similar things and just not saying them when they're sober.
My first name is another issue altogether, and again, this will probably differ as well depending on whether an individual chooses to keep their birth name in katakana, keep their birth name but use kanji as I did, change their name to something derived from their birth name but more Japanese-sounding, or take an entirely different Japanese name.
In my case, no one seems to believe that the kanji version is my only "real" legal name. There are two Itos in my son's class, and whenever there's a need to make a list of parents' names, she always gets listed as 伊藤 (first kanji of her given name in parentheses), and I get listed as 伊藤（キ） instead of 伊藤（琴）. It seems more important to maintain the 和, or group harmony, in those situations than to make a fuss, so I usually let it go, but sometimes I do need to clarify it when there are things like insurance involved, or when we need to prove that we live in this city in order to use the community center, since both city hall and the social insurance scheme only know me by my official kanji name.
I tend to shy away from using my first name, not because it's especially difficult for most Japanese people (it usually isn't), but just because I hate being on the outside when it comes to levels of politeness. I'm never sure if someone's calling me by my first name because they consider me a friend, or just because they're under that mistaken Japanese assumption that Westerners always call each other by their first names, regardless of how well they know each other or what the situation calls for. I usually asked to be called "Taro-kun Mama" (Taro is not my son's actual name, but if you've ever been around little kids and their parents in Japan, you're probably familiar with that form of address!). I am rarely called "Ito-san" at school, but again, there are two Itos, and because of that the other Ito-san really doesn't get called by her last name either, so it's hard to blame that on race or ethnicity at this point.
I have one friend who calls me "Koto-chan," and my husband's best friend calls me "Kin-chan," because the first kanji of my name can either be pronounced "Koto" or "Kin" by itself, but in general I'm either called by my full first name, my last name, or by my son's name plus "Mama."
As an interesting side note, at the restaurant I used to work at I was "Ito-san," just another employee (and no one ever asked me to prove my nationality or that I was ever eligible to work legally in Japan when I was hired either). When I taught English, on the other hand, "Japanese staff" (which included Korean-born Koreans and one Indonesian, basically anyone who looked Asian and spoke decent Japanese) fell under the Japanese system of address, and "native teachers" (including Southeast Asians who didn't speak much Japanese and a few Europeans who were not actually native English speakers) got called by their first names regardless of age, seniority, or anything else. The English school also seemed to have a hard time changing my name to 漢字 (Japanese sinograms) on the income statement I needed for my tax return — they also assumed that my legal name was in カタカナ (Japanese syllabet often used for foreign words), despite the fact that I spelled it out for them in an email and sent them a copy of my Japanese passport as proof that I didn't need to keep sending them renewed copies of my 外国人登録証明書 or "ARC" anymore. It strikes me as a little interesting and a little sad that an organization with an incredibly international staff and an apparent mission of preparing Japanese students for international communication has a harder time comprehending the idea of naturalization than a local family restaurant with a monolingual menu does.
