The IJN retains an Eight-Eight fleet structure

What would the Imperial Japanese Navy's fleet structure look like in the 1930s without treaty limits?

It would probably follow the Eight-Eight concept with sixteen high-quality capital ships, a balanced supporting force, and an increasingly important but uncertain carrier arm.

The alliance reduces the requirement for Japan to match every possible adversary alone. An Eight-Eight structure would provide sixteen high-quality capital ships with a balanced supporting force. That fleet could hold Japan's position until the Royal Navy arrived against a larger coalition. How carriers fit into the structure remains the principal developmental uncertainty.