Tourism visa changed to a work visa?

I am currently still in University and have an interview with ECC later this month, however I really just want to find a smaller, more private company to work at. If I don't have a job by end of August, I still plan to go to Japan and search from within as there are not that many Jobs that hire outside the country. I just want to know, are companies willing to sponsor your visa status change from within the country? I speak conversational near business Japanese, so that's not a problem.

Yes, it is possible and frequently done. However, the process can take several weeks. If it takes longer than your stay of period as a tourist, you might be forced to leave the country temporarily in between.