Looking for logging into the Firefox Sync site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Firefox Sync site. After that you can login as usual with your login credentials.
https://www.mozilla.org/ja/firefox/accounts/
https://support.mozilla.org/ja/kb/how-do-i-set-sync-my-computer
https://support.mozilla.org/ja/kb/sync-bookmarks-tabs-history-and-passwords-android
https://support.mozilla.org/ja/kb/ive-lost-my-firefox-sync-account-information
https://support.mozilla.org/ja/kb/access-mozilla-services-firefox-accounts
https://support.mozilla.org/ja/products/firefox/sync
https://support.mozilla.org/ja/kb/how-do-i-choose-what-types-information-sync-firefox
https://support.mozilla.org/ja/products/firefox/sync-and-save
https://support.mozilla.org/ja/kb/firefox-sync-troubleshooting-and-tips
https://support.mozilla.org/ja/kb/im-having-problems-confirming-my-firefox-account
https://support.mozilla.org/ja/kb/suspicious-activity-my-firefox-account
https://pc.siraberu.info/post-1532/
https://qiita.com/ironsand/items/84eb317f15e525af12a9