SK3 said:
Is it possible to live in Japan?
If so, how?
Just breathe normally. The air is not si different or unique (as they would like to have you believe), and it shouldn't cause foreigners any health risk even with their alien lungs.
Most of food is also edible and actually recommended. Note that only a part of human beings (Japanese included) can ingest a local aliment called "nattou". Just try to see if you body has the right immunity for its consumption. If it hasn't, you shouldn't worry too much about side-effects as your body will automatically reject it as it enters your mouth.
You should beware of policemen, who are preying on gaijin, which they like to acuse to cover their own wicked pachinko business.
Watch out for earthquakes too, and avoid renting an apartment on the lower floors to avoid being crushed once a M8 quake will crush your 'mansion'.
Other notable risks are 'tepodon' and 'tendon' (I heard they were developing 'katsudon' too) launched from the North Korean Empire of Evil, whose leader think he is cool but is in fact a buffoon.
Major health concerns include AIDS (esp. in the Roppongi and Shibuya areas), 20cm long centipedes, biting monkeys, ogres, flying grandmothers and foxes that steal your spirit by entering under your fingers.