A photo I recently discovered on-sale on the Japanese Ebay.
The Navy pilot wears a Model 1929 (Showa 4) uniform. From 1926 until 1929 various uniforms from overseas were tested and this one used a water-proof fabric and zippers imported from France (Japanese didn't manufacture at the time).This design became the basis for all following Navy pilot uniforms. The color was "gray brown".
The seaplane looks to be a Yokosuka E1Y but I have my doubts. What do you think?