[Sangetsu]

Technically speaking, almost all jobs which are worked by foreigners in Japan are part time. My schedule is "officially" 29.5 hours each week (though in my case, I only work about 20 hours a week). On the other hand, most other foreigners who work "part time" usually spend about 40 hours in the office, though the books will show that they only "worked" for 29.5 of those hours.

The reason behind the part time shenanigans is that employers have to pay more for insurance and benefits for "full time" workers. Odds are, if you come to Japan to work, you'll be part time, whether you actually work part time hours or not.