JMSDF Kure Museum is located at, you guessed it, Kure, which is just a short train ride up the coast from the city of Hiroshima.
The museum is dedicated to the art of Mine sweeping, and especially the part that the Japanese Navy has played since the end of WW2. Also, they have a fantastic section dedicated to Submarine's, and they have a real life, bloody huge submarine in the grounds that you can visit and walk around.
The museum is run by the JMSDF(Japanese Maritime Self defence Force), and is free, no charge whatsoever to visit, but they do take donations. They have a coffee