(even on a crowded bus)
In Japan, personal space is often at a premium. People are pretty polite about it, but they do spend a lot of time in your bubble, so here is one way I discovered, somewhat inadvertently, for dealing with it.
It starts with your clothes. Since you live in Japan, you know about the rainy season. You also know about the way that drying your clothes is done by hanging them outside. While clothes dry quickly in hot dry August and take a freezing forever in the depth of January, the combination of heat and humidity you experience throughout June creates the perfect condition for the production of a 'lying shirt.'
A lying shirt is one which, when dry, looks and smells just fine. It also smells just fine when it is still wet but fresh out of the washing machine, laden as it is at that time with the smells of detergent and softener. But get it wet under any other conditions, and it will give off a muted but pervasive funk that will make you wrinkle your nose and look around, wondering if it could possibly be you.
It takes a while to figure out if what you have on your hands is a lying shirt, but once you have one (and by June's end, you should, and after two Junes you definitely should), it will hold true for you even when dried under the August sun. Since August is the hottest, it is also the time when it's nicest to have personal space.
Now, make sure you have all day clear, and get your stuff together for a weekend or overnight trip. Carry all this stuff preferably in a backpack, so you get nice and sweaty. You can leave the backpack in a train locker for this next step.
Find a mountain. I used the hike from Nakayama-dera to its Okunoin, which was described as being a one-hour walk. If you use a one-hour walk, give yourself exactly two hours to complete the round trip and you should be good. This will impel you to book it up the mountain and also back down again. Do this at midday for maximum levels of disgusting; if there aren't white traces of salt on your shirt as it dries, you aren't really trying. Make sure, of course, to stay hydrated -- keep buying those water bottles and Pocari Sweats (I prefer Aquarius, but whatever).
After you return from this endeavor, you should be pretty soaked. Allow yourself to dry off as you move on to your next destination - I used Katsuo-ji in northern Osaka. You get extra points if you work up another sweat, but at this point it isn't really necessary, because your lying shirt should be doing the work for you.
By the time the temples all close at five and you are on your way to stay at a friend's house, you will actually have people moving out of the seat next to you on the bus into seats some distance away. Congratulations!
"Miriam, for the first time since I became homeless, I actually smell like I am." - not the most PC thing I ever said. (She laughed at me because I had thrown my clothes outside onto the balcony and leaped into the shower almost as soon as she opened the door.)
As a side note, I was really tempted to see if a run in a good old American household dryer would cure my shirt of its lyin' ways, but in the end I just couldn't take it anymore and stuffed it in a trashcan in a bathroom somewhere in Miyagi prefecture. True story. Sometimes I still miss it. But not its lies.