Haunting, melodic, melancholic, poetic... many more praising adjectives suit this movie. It marks the birth of Japanese modern cinema. Oshima brilliantly continues the masters Mizoguchi and Ozu, while at the same time marking a big turn in style and themes.
The movie is modern in both: style and themes. I dare saying that this style marked many great contemporary directors (as different as Tarantino, Jia Zhang-KE or Michael Mann). It has, for instance, a questioning and a renewal of the dramatic content that a scene can exhibit. Another novelty in Oshima's style is the manner in which he treats social themes: a mixture of documentary-style and fiction-style, greatly developed later by Jia Zhang Ke, and having an affiliation with the French nouvelle vague (the time overlap is no coincidence).
As for the themes: even if Mizoguchi was already interested in social problems and their reflection upon the individual, he was never so pessimistic as Oshima. Watch the movie and you'll see what I mean. But, in spite of a much more cruel view upon society, Oshima has the same deep message as Mizoguchi: the beauty. You can see it in every scene. Look carefully: there is much light in this dark movie!