Lake Khanka and take photos of the enemy positions and seaside roads. The two aircraft were to have their hinomaru and every other identification marking removed as well as all armament and unecessary equipment. The crew were to have their rank insignia also removed and to be extra careful under no circumstances to make an emergency landing inside Russian territory. If they were spotted by enemy fighters they should escape with maximum speed and if they were shot they should try to fall in the Sea of Japan. Capt Ishiki was quite surprised since this was his first such mission but asking around found out that such flights were done 2-3 times a year. His job as a meteorologist was to let the pilots know of a day with nice weather suitable for the flight. The altitude was to be between 9,000-10,000 meters to avoid the aircraft being detected. But photography from this high altitude required perfectly clear skies from any clouds that would obstruct the view. Another consideration was the fires set by farmers that created huge billows of smoke, therefore the flight was to take place before noon. Special German Zeiss cameras were carried by the planes and the intelligence department took extra care to receive the weather forecast from the Russian side, which was easy to decipher.
Capt Ishiki left the headquarters in Changchun for Dunhua, the base of the aircraft, and stayed there for a week until the weather was finally perfect for the mission. During that time the planes and their crew were on stand-by and when Ishiki gave the go ahead they rushed to their mission. The Soviet border was too close from Dunhua so "Dinah" number #1 had to fly back to Changchun to reach the altitude of 9,000meters. "Dinah" number #2 tried to cross the border from lake Khanka but when both aircraft were near the border they noticed that they were leaving massive contrails behind them that could be spotted from the ground. So "Dinah" #2 abandoned the effort while #1 continued hopping that the contrails would not be noticed.
Near Vladivostok "Dinah" #1 started taking photos of the enemy lines when pilot captain Sato ordered his observer to put on his oxygen mask. "Why? What happened? Are we to fly higher?" asked the observer. "Look down" replied Sato and two Soviet I-16 were fast climbing to intercept them. The Japanese crew had two options, either to escape back to Manchukuo or towards the Sea of Japan. They chose the second and just when the I-16 were about 300meters behind them, they broke the engagement leaving "Dinah" alone to make a big semicircle and re-enter Japanese air space in Chongjin in (North) Korea. Flying at an altitude of 3,000meters the plane was quickly spotted by the ground forces setting off the alarm about an aircraft without any markings but only briefly.
Later it was discovered that it was air defence day in Vladivostok and perhaps the Soviet aircraft didn't carry ammunition. Russian diplomatic protests were expected for this border incident but none was placed perhaps because Soviet aircraft also regularly performed similar missions especially over Dalian.
Source: "Maru" November 1976, issue #363