Hi, indeed Japanese and I believe it reads; 純銀 pure silver. The other mark could be a maker's/retailers mark unknown to me. Congratulations, nice looking sake set made out of pure silver.
Peter
Source; World Hallmarks Volme II Asia, Middle East, Africa
The sake set is made in the Heisei period 1989-present
One of the characteristics of silverware in Japan is that it is tarnished. This is the spirit of Wabisabi — the beauty found in things being naturally shifted .