Hi there,
On this route a 14 day JR Pass be very cost efficient and cover travel between all the cities you plan to visit. I don't think you'd need any further pass, though I do recommend getting a Suica card (or similar) to pay for any local travel that may not be included.
I wrote a station access guide for the Japan Rail Pass a little while ago, for each station during the RWC 2019.
Sapporo Dome
There is no JR Station near the Sapporo dome. Visitors can use the JR Sapporo Subway line from Sapporo Station to Fukuzimi station (¥250 / 26 minutes) and walk from there in 12 minutes to the Sapporo dome. There are clear signs along the way. There is also an express bus between New Chitose Airport and the Sapporo dome.
Kamaishi Recovery Memorial Stadium
The station for this station is called Unosumai and is still begin rebuild after the big Tohoku earthquake. The station is planned to be reopened before the RWC and will be served by the Sanriku Railway. JR Pass users can use the Shinkansen to travel to Morioka, then transfer to a local JR train to Kamaishi and finally the Sanriku Railway to Unosumai station. The local train from Morioka takes about 2-3 hours to Unosumai.
Kumagaya Rugby Stadium
The closest JR station is Kumagaya station, which is located on the Hokuriku Shinkansen for fast access from Tokyo. From Kumagaya stations, local buses run in about 20 minutes to the stadium (Kumagaya Sports Bunka Koen Rugby Ba Bus Stop).
Tokyo
Also known as Ajinomoto Stadion, Tokyo stadium is within walking distance from Tobitakyu station on the Keio line. The Keio line is not covered by the JR Pass but JR Pass users can use the JR Pass to travel to Shibuya station, then use the Keio line from there, taking 30 minutes / ¥ 240.
International Stadium Yokohama Stadium
Also known as the Nissan stadium, it can be reached in 10 minutes on foot from Shin-Yokohama station. Shin-Yokohama both has local JR lines and is on the Tokaido Shinkansen for easy access with the JR Pass.
Shizuoka Stadium Ecopa
This stadium can be accessed on foot from JR Aino station on the JR Tokaido line. The closest Shinkansen station is Kakegawa, from where it is only 4min by local train to Aino station. Alternatively, local JR lines run in about 25 minutes from Shizuoka station.
City of Toyota Stadium
This stadium can be reached on foot from Toyotashi station on the Meitetsu-Mikawa line. Meitetsu is a so called 3rd sector railway and does not accept the JR Pass. JR Pass users are advised to use the Shinkansen to Nagoya station, then use the Meitetsu to Toyotashi, taking ¥ 760 / 50 minutes.
Hanazono Rugby Stadium
The closest station on Hanazono Rugby Stadium is Higashi-Hanazono station on the Kinketsu Higashi-Hanazono line. Kintetsu is not covered by the JR Pass. JR Pass users can use the JR Pass from Osaka to Tsuruhashi on the Osaka Loop line, then transfer to the Kintetsu Nara line to Higashi-Hanazono (260yen / 16 minutes).
Kobe Misaki Stadium
Kobe stadium can be reached on foot from Wadamisaki on the JR Sanyo Main line and can be reached from Sannomiya station (the main JR station in Kobe) by local JR train. Alternatively, Wadamisaki is also on the Kobe Subway Kaigan line.
Fukuoka Hakatanomori Stadium.
The closest JR Station is called Sue station on the JR Kaishii line. JR Pass users can use the Shinkansen to Hakata station, then a local JR train to Sue station. From here walk 5min to Tabiishi Hachiman(Shrine) bus stop. From here Line 3 takes you to Higashihirao Koen-iriguchi(Park), taking 14 minutes / 230yen.
Alternatively, the stadium can be reached by bus from Fukuoka airport.
Kumamoto Stadium
This stadium can be reached in about 30 minutes walk from Kumamoto station. Kumamoto station can be reached by JR Kyushu Shinkansen. Customers who fancy less of a walk can take tram line B to Daniyamamachi Station and from which it is a 5 minutes walk.
Oita Stadium
Also known as Oita Bank Dome, there are special shuttle buses available from Oita station to this stadium.
For travel between cities, normal planning tools like Hyperdia are recommended:
https://www.jrpass.com/blog/plan-with-the-hyperdia-online-timetable
Hope you find it useful,
Daniel
