How to get there

http://www.hyperdia.com/en/ (Hyperdia) is a convenient search engine that provides complete timetable of all transportation routes in Japan.
JR East Infoline, 050-2016-1603, is a telephone-based service providing JR East transportation information in English, Chinese and Korean from 10am to 6pm, daily except during the new years’ holidays. https://www.jreast.co.jp/e/customer_support/infoline.html

From the Tokyo area: The Joetsu Shinkansen makes frequent trips daily to Niigata and takes about 2 hours. Bus access to the Sado Kisen Niigata Port leaves from the terminal #3 at JR Niigata Station, Bandai Exit. (Note: The terminal is also used by other buses bound for other places.) English speaking staff members at Tourist Information Center at Niigata Station Bandi Exit (025-241-7914) will help you if you need the language assistance.

From the Osaka/Kyoto area: JR West offers daily rail service to Naoetsu or Joetsumyoko. Access buses leave from Naoetsu Station and Joetsumyoko Station East Exit bound for Sado Kisen Naoetsu Port.

Sado Niigata Pass (5,000 yen for adults, 2,500 yen for children 6 to 11 yrs old ) is available to holders of JR East Pass (Nagano, Niigata area).
These passes include:
1) a set of round-trip coupons for Sado Kisen ferry (Niigata Port – Ryotsu Port),
2) one three-day fixed route bus pass on Sado, and
3) a set of round-trip tickets for bus services between the JR Niigata Station and Sado Kisen Niigata Port.
Note:
The pass can be purchased before visiting Sado Island only with cash in Japanese yen at the following offices
– Tourist Information Center at JR Niigata Station Bandai Exit
– Sado Kisen Niigata Port Information Center
Other pass options may be available. For update information, visit: https://sado-pass.visitsado.com/

Highway and overnight buses are usually the less expensive way to travel.
https://www.kosokubus.com/en/ (Kosokubus.com) is an on-line search engine for express bus services.

Sado Kisen runs ferry services daily from Niigata to Ryotsu (2hrs and 30min, or 67min by jetfoil) and seasonally from Naoetsu to Ogi (75min by jetfoil).
025-245-1234 (Niigata Information Office)
0255-44-1234 (Naoetsu Information Office)
Sado Kisen Ferry Schedules in English

・Tokyo Station: 7:30am – 8:30pm
・NRT Airport: 8:15am – 7:00pm
・HND Airport: 6:45am – 6:30pm Wi-Fi accessible.
http://www.itcj.or.jp/en/index.html

03-3201-3331 (9:00am – 5:00pm daily)
The organization gives you comprehensive information of touring throughout Japan.
JNTO Tourist Information Centers (throughout Japan)