Originally Posted by
freecia
Some do offer seat reservations with JR Pass via internet
JR East
https://www.eki-net.com/pc/jreast-sh...Menu/Menu.aspx
JR Kyushu
https://kyushurailpass.jrkyushu.co.jp/reserve/TopPage?3
JR West offers online reservations for JR West regional pass holders. National pass holder reservations are slated for 2019
You will find that some things in Japan are not enabled for easy access via the internet and limited in non-Japanese language support. For example, bus schedules are much easier to get in Japanese than English. At least there are some common highway bus route mandatory reservations available now. Restaurant reservations are another.
Thanks a million yen! You might consider adding that to the wiki in this large thread.