Japan, up to 2 years of Tax Treaty

(Reported from Internal Revenue Service (IRS), US government Publication 901)

Tax treaty for Professors, Teachers, and Researchers

An individual who is a resident of Japan and who is temporarily in the United States primarily to teach or engage in research at a university, college, or other recognized educational institution is exempt from U.S. income tax on income for the teaching or research for a maximum of 2 years from the date of arrival in the United States.

The exemption does not apply to income from research carried on mainly for the private benefit of any person rather than in the public interest.