From MangaHelpers:
A mysterious masked and armored man has been showing up in Tokyo, apparently fighting criminals in the name of justice. He won't be able to clean up the city alone, though, and he is looking for partners.
Satou Yuuki is a kind-hearted high school student who is being brutally bullied by a boy from a powerful family and his friends. Yuuki's rage is buried so deeply inside himself that it becomes another personality, composed only of anger. When the bullies push him too far, Yuuki comes to the surface, and only the armored stranger keeps him from becoming a murderer.
Suzuki Akari is an unattractive girl in the same school, who is treated badly by everyone. At night, though, she makes herself up into a pretty girl and lets out her rage and tremendous strength on gangsters and rapists.
The masked man encourages Yuuki and Akari to join him in cleaning up the crime of the city and to use their strength to fight for justice. The three of them are surely going to have their work cut out for them.