Review of Absolute Duo

(NO SPOILERS) After watching the entire anime I still have absolutely no clue what an absolute duo is supposed to be. It is some sort of bond between to people so they are strong, but why? Are they supposed to be superheroes? Soldiers? Villains? Mercenaries? What do they do after they finish school? There was a weird episode transition, where one episode they were going to fight a group, and the episode ended with the group being in an arena saying "come fight us" or something along those lines. But the next episode started in an abandoned mall, and they were attacked by random soldiers? Andone character, who was supposed to be good, started fighting the protagonist and shot him. But when that character got arrested by the soldiers, the protagonist wanted to save her? Even though she just shot him?
There is almost no continuity, characters randomly disappear and appear, locations randomly change, characters suddenly become good or bad? But it's still fun to watch overall.