The fishing boat was chartered by the Maritime Self-Defense Force and was wary of other vessels from approaching during the performance test of Oyashio.

[2] On 8 December 2009, the Kagoshima Maritime Security Department sent documents to the Captain and three others on suspicion of the risk of a possible traffic incident.

Furthermore, at around 0:15 pm on 17 June 2009, during training on the Pacific Ocean about 28 kilometres (17 mi) East of Shiriyazaki, a cable for resource exploration (4.8 km) towed by the Agency for Natural Resources and Energy research vessel Shigen [ja] (10,395 tons) of the Ministry of Economy, Trade and Industry caused an incident that left some of the crew injured.

On 3 April, she entered Subic Bay on Luzon Island, Philippines, facing the South China Sea.

[6] She had been in service for 25 years, the longest period attained by any MSDF submarine, and she had travelled 500,000 kilometres (310,000 miles) in distance.