[jasonbvr]

Once you find an employer, they would give your contract to the immigration office and apply for a change of visa status. The only way you would have to leave Japan is if you don't have enough time on your current visa to stay in Japan until the work visa is issued. If that is the case, I would ask for a change to a tourist visa at the immigration office before you left and came back. But no, you don't have to leave Japan to get the work visa granted as long as you are on a valid visa.