I am someone who believes in condoms always and testing regularly. It doesn't matter how safe you are or whether or not you have a boyfriend/girlfriend or what kind of lifestyle you lead. If you have sex, you should test for HIV and STDs. It is part of being a socially aware, responsible modern person.
C'mon guys, free HIV tests at the Tokyo Metropolitan Health Clinic!
GETTING TESTED FOR HIV IN JAPAN IS EASY EVEN IF YOU ARE A FOREIGNER. There is an HIV Testing Center close to the South Exit of Shinjuku Station that gives free and anonymous tests to anyone, complete with English versions of all necessary paperwork. I just went the other night. I will post more information in the comments, and I invite you to share any information you have about HIV/STD testing and related health matters in Japan.
If you're embarrassed about getting tested or think it's weird, you need to stop being dumb and get in the now. I get tested and talk about it because I want to express that it's a normal and healthy thing to do. A few years ago, the actress Scarlett Johansson said in an interview that she gets tested for HIV twice a year. People made a huge deal out of it and everyone framed the quote like, "Johansson denies promiscuity yet admits getting frequent HIV tests." What fucking year are we in? Things like this remind me that many people are still dangerously uptight about sex. I've had girl friends who didn't carry condoms because it made them feel slutty, and I've known plenty of sexually active people who don't get tested because they associate it with admitting to a dirty lifestyle.
Scarlett Johannson made no apologies and still insists, "It's part of being a decent human, to be tested for STDs. It's just disgusting behavior when people don't. It's so irresponsible." Evidently she is comfortable with her life and not ashamed of taking care of it. I'm glad I can say the same and I hope you can, too.