At about 15:34.5 hours the Skipper assessed that there was a risk of collision as the "Nadashio" approached to about 29｡?n his port bow one mile off. While he was watching the "Eve I", which was observed about 10｡?n his port bow 1,600 m off, and the "Nadashio" developing a close quarters situation with each other, the situation evolved and at 15:36 hours the "Nadashio", located on his port bow about 1000 m off was to pass ahead of the "Eve I". Observing this development of the situation, he reduced her speed to half ahead of about 7.3 knots and changed over the steering mode to manual with the intention to let the submarine pass ahead of his boat.
At about 15:37 hours, the "Nadashio" approached to a distance of about 500 m, but the Skipper continued to proceed without taking evasive action, such as promptly taking her way off or altering her course to starboard. Slightly before 15:38 hours, when the distance decreased to about 120 m, the Skipper, not noticing the starboard swing the "Nadashio" was making, and estimating that there still remained 200 m, put the rudder hard over to port and reduced her speed to slow ahead engine while sounding two short blasts with the intention to clear of the stern of the submarine. His attempt, however, was in vain, resulting in a collision at a speed of about 6 knots when she was headed on about 120°.
Since both "Fuji Maru No.1" and "Nadashio" had still headway upon collision, the bow of the former ran up onto the bulb-like bow of the latter, making the stern steeply sink below, accompanying a great list and resulting in her turning turtle on the side. As a result, sea water rushed into the pleasure fishing boat through the access doors kept open on the port side of the crew space, fishing gear store and aft part of the internal passage, allowing crew members no time for directing and guiding passengers to safety, and sunk the boat at a position about 108.5°3,250 m from the Yokosuka NE Breakwater East Light at about 15:40 hours.
Crew members in the vicinity of the bridge and ten plus passengers in the saloon on the upper deck escaped from the ship as a result of falling overboard or jumping into the sea, and drifted while holding on to floating objects like styrene foam and waited for rescue operations. Three persons in total, namely, the Skipper, one crew member and one passenger, boarded onto an inflatable liferaft floating nearby, but other passengers and crew members who were inside the ship, such as in the passenger room and the saloon, were trapped inside and were unable to find their way out.
On the other hand, the Commanding Officer of the "Nadashio" issued an order to muster crew members for rescuing men overboard at about 15:39 hours, and made a request by radio telephone for assistance from the "Chitose" which was sailing ahead of her. He reported on the collision with a fishing boat to the Commander of Submarine Flotilla 2, who was on board the "Setoshio". He did not let other vessels sailing in the vicinity know of the accident by issuing a distress signal nor did he notify the Maritime Safety Agency of the occurrence of the accident. Thereafter, he gradually approached the scene by using the engines variously and engaged in rescue operations by ordering crew members in stations to deliver rubber lifeboats and to make efforts to discover men overboard.
At about 15:46 hours, the "Nadashio" rescued directly onto her one person who was drifting while clinging to a lifering and then saved another person from a life rubber boat and transferred that person to a launch of the "Chitose", and recovered another person safely by sending a swimmer from the submarine.
