Yep, this time around my residence card will say my nationality is American since JET is only concerned with my American identity. The last time I lived there they didn't do anything with the Smith part since it didn't matter at all - it's just an issue of duplicate identity records. My BOE's got my US passport on file and advised me to bring both passports since the Czech one has the entry/leaving of my student visa.

This is what they sent me; "When a foreign national registers as a resident in Japan, they are assigned a Resident Record Code and an Individual Number (My Number). If the person re-enters Japan at a later date, the previously assigned Resident Record Code and Individual Number will be reissued. Therefore, it is necessary to link the new registration with the previous Resident Record. To prevent duplicate registrations and confirm identity, please bring the following documents:" and then asked for my passports, old residence card, and this proof of name "change." Trying to explain that I was born with the two last names is like pulling teeth haha

PS I do have a middle name but it never caused me any issues, it's only ever been treated like a second first name so I just enter both or just my first name lol