Helpful links:
https://travel.state.gov/content/passports/en/alertswarnings/north-korea-travel-warning.html
https://china.usembassy-china.org.cn/
Sources (includes links above):
https://cpj.org/2015/04/10-most-censored-countries.php
https://freedomhouse.org/report/freedom-world/2016/japan
https://freedomhouse.org/report/freedom-world/2017/china
https://freedomhouse.org/report/freedom-world/2016/north-korea
http://www.bbc.com/news/world-asia-pacific-15289563
Credits: Jay Perez is the sole contributor to East Asian Borders. Jay is the lead researcher, programmer, and organizer.