Kubo Ibuki

I haven't read the source material, but it's pretty clear that the unnamed enemy is the People's Liberation Army.

This movie has what could have been interesting subjects: The threat of China and the militarization of Japan. But it just deal with them in a very caricatural way.

It also fails as a pure entertainment movie, the action is very slow, characters are irrational. They still have a moral dilemma to fight while missiles rain on them.