I'm sure most people here were already aware of the new submarine class, but thought I would share. On the basis that Japan is planning to have 22 submarines in service, the submarine fleet will eventually be:
(2 training submarines - Oyashio)
6 Oyashio (older boats decommissioned)
No doubt more Taigei submarines will be built to replace the last of the Oyashio subs when they're eventually decommissioned.