Most of the daily conversations are based on student life, but Japanese-specific phrases and idioms frequently appear. From the perspective of learning Japanese, students and youth speak the majority of the lines, and it is fortunate for Japanese learners that honorifics and slang do not appear.
The content of the conversation is not too difficult, but there are many topics of mafia struggle and revenge, so it is an animation for advanced users in terms of learning Japanese. However, it is difficult to recommend.
The two heroines are high school girls, but because there are many adult conversations, difficult phrases and high-level honorific words often appear. Because of the world view of the work, there are many youkai and police-related terms, so if this anime is really suitable for learning Japanese, it is limited to advanced learners of Japanese.
Anyway, the number and lines of the leading role Subaru are very large. Individual characters will not be heard because they speak differently from the present day. It is a very difficult anime for learning Japanese.
It is an anthropomorphization of the Japanese fleets during the Second World War made into a character of girls named “艦娘” (かんむす, kanmusu) . Because there are so many characters, there are many Kanmusu who speak in a distinctive way of speaking which leaves an impression for each characters.
As you can see in the title of this anime, there are many lines specific to “中二病” (ちゅうにびょう, Eighth Grader Syndrome). Chunibyo is a slang, which they believe that they possess supernatural powers and behave so. The word “中二病” is attached as “病” (びょう, disease) but it is not a real disease. Since it is close to the behavior of adolescent boys and girls in 2nd junior high school students (中学二年生, ちゅうがくにねんせい), it is called “中二病” (ちゅうにびょう, Eighth Grader Syndrome). Watching this anime helps your understandings about the concrete Chunibyo words well. From just the viewpoint of learning Japanese, this anime will not be good. (But, repeatedly, this is an outstanding anime!)