The best choice varies with your requirements and expectations.
How many channels do you need? Which, if any, instruments will you run through the PA. How loud do you need to play?
For intimate settings, stick PAs tend to be less obtrusive. Many of them have built in mixers. There limitation is most of them don't play very loud. Also the way they disperse sound is a bit different than a traditional cab with a woofer and tweeter. There are advantages and disadvantages.
No idea what you can get in Japan or what gear will be compatible with their 100V AC. The EV Evolve 50 seems well respected and is rated for 100V to 220V AC. But it's fairly expensive and does not have much of a mixer. Max SPL is 127dB. I believe this is peak, so continuous will be 121dB. For comparison a QSC K8.2 is rated 128dB peak and 122dB continuous (also rated for 100V to 220V). The Evolve 50 will be fuller and play lower as it has a 12" sub. Most likely you would want to put the K8.2 on a tripod.
Note: If you consider buying one of these in the US and transporting it to Japan, make sure it's auto-switching to whatever the line voltage is.
Rather than an all-in-one, I would probably go with a separate powered cab (or 2) and a mini-mixer. The Behringer Flow 8 looks tempting IMHO, assuming you are interested in learning how to integrate it with a phone or tablet. The Flow 8 is digital, so it will have a lot more processing power than a small analog mixer. The down side is you have to learn to use.
Does it make more sense to rent?