The victory enabled Russia to stay in first place of the group with a 4-0 win-loss record and the full 12 points. Japan dropped to a 2-2 mark and 6 points.
The Russians, who led 15-6 in blocks but trailed 10-5 in aces, also had veteran Evgenia Estes in double figures in the scores with 11 tallies.
Gamova finished with five blocks and Goncharova, Estes, Maria Perepelkina, Maria Borisenko and Iulia Merkulova had two apiece.
Saori Sakoda and Saori Kimura each finished with 23 points for the defeated side.