Coming from 2011, and consisting of 12 episodes, Ga-Rei: Zero is an anime prequel to the manga series Ga-Rei by Hajime Segawa. I don’t read manga (mostly because I’m illiterate), so I had no idea what to expect going into this.
The Ministry of Defense has a secret unit known as the Supernatural Disaster Countermeasure Division, whose job it is to defend Japan from all sorts of paranormal bad guys. The first episode shows a unit killing some deadly monsters, and that first episode was incredible. The characters were really interesting, they were all mature adults (rare for an anime), and they seemed to have an intriguing back story. Plus, the animation was outstanding. This had to rank up there with some of the best single-episode animation quality of all time.
And then, once the unit returns from their successful mission, they get slaughtered. SURPRISE! The characters I just invested a half-hour in all got murdered. TROLLING! What remains is some mysterious teenage girl with a katana, who killed them all. That intriguing back story? Never mentioned again. It was just a way to further troll the viewers into thinking these characters would be important, just to extract shock value when they suddenly died.