While ten of the twelve Soryu boats (84 metres, 4,200 tonnes submerged) are still equipped with Saab Kockums' air-independent propulsion system and only the last two of the series from 2020 have been fitted with lithium-ion batteries for propulsion, the Taigei boats (85 metres, 4,300 tonnes) developed from this class are exclusively battery-powered.

"Sougei", the sixth and penultimate boat in this class, was launched in mid-October at Kawasaki (KHI) in Kobe. Launched in March 2023, "Sougei" is scheduled to enter service by mid-2027 at the latest. For KHI, it was already the 32nd submarine to bear this company stamp.

With the seven boats of the Oyashio class, which date back to the 2000s and have already been modernised, Japan currently operates over twenty 3,000-tonne submarines.