What's the plural form of jidaigeki? Here's the word you're looking for.
Answer
The noun jidaigeki can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be jidaigeki.
However, in more specific contexts, the plural form can also be jidaigekis e.g. in reference to various types of jidaigekis
or a collection of jidaigekis.