Visas

...or more specifically 'statuses of residence'. Whichever term you apply the reality is that if you are a non-Japanese you need permission from the Japanese government before you can work legally. Another reality related to visas is that when it comes to Japanese Immigration authorities everything is seemingly decided on a case-by-case basis so don't take anecdotal tales as fact. If in doubt seek professional advice, or best of all ask at the Immigration information desk. Trust me, the immigration staff are there to help...really, they are.
Below are the main types of visa briefly explained:

Working Holiday Visa

Good news if you're a citizen of Australia, Canada, Germany, France, New Zealand, Republic of Korea, or the United Kingdom and between the ages of 18-30 years old you can apply for a Working Holiday Visa. The visa is good for six months and can be extended for a further six months by the immigration authorities.
Due to its specific time limit, i.e. one year, the Working Holiday Visa is often frowned upon by some employers and it's not unusual to see recruitment advertisements stating 'no Working Holiday visa types'. Not to worry as many more employers see this one year limit as a blessing.

Working Visa

This is the real McCoy. The 'full working visa' term actually covers a wide range of visa types tailored to specific industries. Surprisingly the visa issued for most English teachers is not the 'Instructor' visa, which covers language instruction at schools and educational establishments but rather the 'Specialist in Humanities/ International Services' visa which is used for those who are employed because of their specific ways of thought based on experience with a foreign culture, amongst other things. Issued for either 1 or 3 years and relatively easy to re-new. Your company will normally sponsor this visa for you so it means that you must be in full-time employment to meet the criteria for sponsorship.
Note: If you change employers during the course of your visa you are obliged to ask the immigration authorities for permission before jumping ship.

Dependent Visa

For all intents and purposes this is often referred to as the 'spousal visa'. Probably the easiest status to achieve, and once granted you are free to work wherever and for whomever you please or not work at all. The choice is yours. The only disadvantage, as we see it, is that you must be married to a Japanese citizen...
Only joking...

Issued for anything from 3 months to 3 years and readily renewable as long as you remain married.

Further Information

Of the course the above is only a brief overview of the types of visa available. For more specific information we suggest you take a look at the Ministry of Foreign Affairs of Japan website at www.mofa.go.jp  Here you'll find full details of each status of residence plus a list of the documents required when applying. If you're outside of Japan then I'd recommend contacting your local Japanese embassy or consulate who will be able to provide further guidance.