It is theoretically possible, but in reality, not a risk. No one has been infected with HIV in the 40+ year history of HIV from tattoo ink. Also, a shop that takes the precautions you mentioned is NOT going to be putting people at risk for HIV - or Hep C, which is far more common and easier to get infected with. I'd forget about this entirely and not test. You're not going to be the first person infected this way.
I did google around and found only very old 2005-2009 concerns. Only recent one about tattoos are from men’s health website under hiv 6 things you didn’t know about it living in ink and combining everyone’s blood then going into open wounds.
Can’t find any case stuff though like you said so that’s good. Guess I was more worried about foreign places that may not be up to date.
Why would you assume that a tattoo place in Japan wasn't using proper sanitary practices? Japan is one of the few (if not the only) first world country in asia. They are technologically more advanced then most other countries in asia.