to get a working visa you need to have a COE ( Certificate of Eligibility) from the Japanese Govt. This will be applied by your company. And can only be applied in Japan. You will be the one to provide your host company with the requirements but the host company will be the one to apply it for you.
One requirement for the COE is your college records. Working visa are categorized into different levels -->
MOFA: A Guide to Japanese Visas - Types and Categories of Visa
Once you received you have you COE , you can now apply for a visa at your respective Japanese Embassy -->
MOFA: A Guide to Japanese Visas - Visa Applications
refer to links above for all the detailed information.