3-5 months working in Japan

I am looking for opportunities to work in Japan for 3 to 5 months. I'd like to teach English but it seems all the companies require you to agree to a year-long contract. Does anyone know of any opportunities for more short-term work? Or any ideas of where I could look? I have a BA and Intermediate Japanese language ability. I studied abroad there in college for 4 months and would like to go back but don't want to have to commit to living there for more than a few months.
Any ideas?

Since employers have to sponsor you to get you a work-permitting visa, they are unlikely to hire for a very short term, unless, that is, you are eligible (age and nationality requirements) for a working holiday visa. WIth this visa, you can look around for more short-term job - the purpose of the visa being giving young people from overseas opportunities to travel extensively in Japan while providing some way to find casual work to help with the travel expenses.