Battle Royal High School [真魔神伝 – バトルロイヤルハイスクール Shinmajinden Batoru Royaru Haisukûru] (1987)
Starring Kazuki Yao, Kazuhiko Inoue, Hideyuki Tanaka, Chieko Honda, Mari Yokoo, Sakiko Tamagawa
Directed by Ichiro Itano
Despite the similar title and high school setting, this is not to be confused with Battle Royale. They are two very different stories. Battle Royal High School starts off like a martial arts film, with a protagonist that beats the crap out of a karate class and aspires to conquer every dojo in the country. But it quickly transitions to a demonic invasion and accelerates into the realm of pure absurdity.
The plot is tricky to pin down. It’s convoluted and low on explanation, but I’ll try to sum it up. Ryoudo, martial arts champion of his school, gets possessed by a demon trapped on Earth. After that, a demon hunter tries to kill him. Then add in the sudden arrival — from space, I guess — of a space-time continuum inspector who’s searching for the source of a “hyper-psycho-kinetic-wave.” He’s also tricked out with an awesome suit of robot armor. Obviously. And apparently fairies are trying to take over the world by mutating people into hideous monsters. Somehow all of that gets twisted into a plot that actually makes a good deal of sense in the end, as long as you don’t question it.