Travelers should review and follow the Centers for Disease Control’s guidelines for the prevention of coronavirus if
they decide to travel to Japan.   If suspected to have Coronavirus in
Japan, you may face travel delays, quarantine, and extremely expensive
medical costs.  

If you travel to Japan, you should:

• Avoid contact with sick people.
• Discuss
  travel to Japan with your healthcare provider. Older adults and
  travelers with underlying health issues may be at risk for more severe
  disease.
• Avoid touching your eyes, nose, or mouth with unwashed hands
• Clean
  your hands often by washing them with soap and water for at least 20
  seconds or using an alcohol-based hand sanitizer that contains at
  60%–95% alcohol. Soap and water should be used if hands are visibly
  dirty.
• Enroll in the Smart Traveler Enrollment Program (STEP) to receive Alerts and make it easier to locate you in an emergency.
• Follow the Department of State on Facebook and Twitter.
• Review the Crime and Safety Report for Japan.
• Prepare a contingency plan for emergency situations. Review the Traveler’s Checklist

See https://www.cdc.gov/coronavirus/novel-coronavirus-2019.html for additional guidance.