A. You can NOT work in Japan under the status of "short-term" visa.

The applicable for short-term visa is set as follows.

"Sightseeing, recreation, sports, visits by relatives, tours, participation in classes or meetings, business contacts and similar activities that stay in Japan for a short period"

Since there is no word of employment or working here, it is a violation of the Immigration Act Laww to work with a short-term visa (such as those who came with No Visa).

However, you can do a lecture or a presentation without fee.
Or an internship of 90 days without fee is permitted.

Sometimes there are foreigners who enter to Japan with short-term visa for job hunting; i.e. no visa entering.
To make a contract with the foreigner and immediately let him work at the company is to touch the law.

Even if you make contract with a company, you first need to apply for COE(CERTIFICATE OF ELIGIBILITY) application and obtain a new visa permission.

If one works with a short-term visa, it is illegal.

And not only the foreigner activate a crime, but also the company activate a crime for an illegal employment.