This is the DOCOMO Galaxy S20 5G SC-51A User Manual in Japanese provided by the manufacture.
Galaxy S20 5G 取扱説明書[SC-51A]
Samsung official recently revised the user manual for DOCOMO Galaxy S20 5G SC-51A smartphone.
Last December, Samsung officially released the Android 11 update for the DoCoMo versions of the Galaxy S20 SC–51A.
In order to reflect the changes in the Android 11 OS Update, Samsung published the Android 11 version manual for the Galaxy S20 SC–51A..
From the below link you can download Galaxy S20 5G 取扱説明書[SC-51A] Revision 1.0.